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Transfusion efficacy of ABO major mismatched platelets PLTs in

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					                                    TRANSFUSION PRACTICE


Transfusion efficacy of ABO major-mismatched platelets (PLTs) in
        children is inferior to that of ABO-identical PLTs

Friedgard Julmy, Roland A. Ammann, Behrouz Mansouri Taleghani, Stefano Fontana, Andreas Hirt,
                                    and Kurt Leibundgut




                                                              I
                                                                    n everyday transfusion practice, inventory manage-
 BACKGROUND: ABO major compatibility is essential                   ment pressures associated with the limited 5-day
 in transfusions of red blood cells but is not requisite in         storage period for platelets (PLTs) result in the pro-
 PLT transfusions. In adults there is some evidence that            vision of many ABO-mismatched PLT transfusions.
 transfusion efficacy of ABO blood group–identical plate-     To minimize PLT outdating, it is standard practice in
 lets (PLTs) is superior to major-mismatched PLTs.            many transfusion services to administer the oldest PLTs
 However, in children this question has not been investi-     first. These include transfusion of PLTs that are ABO-
 gated for more than 30 years.                                unmatched. While for red blood cell (RBC) transfusions,
 STUDY DESIGN AND METHODS: In a prospective                   ABO major compatibility is mandatory, both AABB and
 study, the efficacy (based on the 1-hour percentage of       the British Committee for Standards in Haematology
 PLT recovery [PPR1hr]) of 400 eligible ABO blood             suggest, but do not mandate, transfusion of ABO-matched
 group–identical or out-of-group apheresis PLT concen-        PLTs.1,2
 trates (APCs), transfused mainly prophylactically to 50           PLTs express ABH blood group antigens on their
 children with hematologic malignancies, solid tumors, or     surface, some of them at very high levels.3-6 After ABO
 aplastic anemia was investigated. The primary objective      major-mismatched transfusions, transfused PLTs may be
 was to compare PPR1hr between ABO-identical and              directly affected by the recipient’s isohemagglutinins, the
 major-mismatched transfusions.                               naturally occurring ABO antibodies, leading to premature
 RESULTS: After ABO major-mismatched transfusions,            destruction of the transfused incompatible PLTs. Further-
 PPR1hr was significantly lower than after ABO blood           more, transfusion of ABO minor-incompatible PLTs stored
 group–identical transfusions (median 21% vs. 32%;            in plasma containing anti-A and/or anti-B antibodies can
 p = 0.034). Multivariate analysis showed major-              lead to a hemolytic transfusion reaction in the recipient.7-9
 mismatched transfusions to be significantly more often
 unsuccessful than identical transfusions (odds ratio
 [OR], 3.97; 95% confidence interval [CI], 1.52-10.39;
 p = 0.005). Using flow cytometry and fluorescent               ABBREVIATIONS: APC(s) = apheresis platelet concentrate(s);
 microscopy, it could be demonstrated that PLTs of            BSA = body surface area; BW = body weight; CCI1hr = 1-hour
 subgroup A1, significantly expressing A antigen on their      correct count increment; LME = linear mixed-effect (modeling);
 surface, were rapidly cleared from the circulation of        PPR1hr = 1-hour percentage of PLT recovery.
 group O or B recipients. In contrast, major-mismatched
                                                              From the Department of Pediatrics and the Department of
 transfusions of A2 PLTs, expressing no detectable A
                                                              Hematology, University of Berne, and the Blood Transfusion
 antigen, were as successful as identical transfusions
                                                              Service of the Swiss Red Cross, Berne, Switzerland.
 (OR, 1.13; 95% CI, 0.16-7.88; p = 0.90).
                                                                    Address reprint requests to: Kurt Leibundgut, MD, Division
 CONCLUSION: These data clearly indicate that in chil-
                                                              of Pediatric Hematology/Oncology, University Children’s Hospi-
 dren ABO major-mismatched PLT transfusions result in
                                                              tal, CH-3010 Berne, Switzerland; e-mail: kurt.leibundgut@
 inferior transfusion efficacy, with the only exception of
                                                              insel.ch.
 group A2 PLTs. ABO minor-mismatched PLTs showed
                                                                    This work was supported by the Swiss Cancer League
 comparable efficacy to identical transfusions.
                                                              (Oncosuisse, Berne, Switzerland; Grants OCS 01470-02-2004 and
                                                              KLS-01828-02-2006).
                                                                    Received for publication May 26, 2008; revision received
                                                              July 14, 2008; and accepted July 17, 2008.
                                                                   doi: 10.1111/j.1537-2995.2008.01914.x
                                                                   TRANSFUSION 2009;49:21-33.


                                                                              Volume 49, January 2009      TRANSFUSION 21
JULMY ET AL.



     Already in 1965, Aster10 demonstrated that ABO           ences in transfusion efficacy, measured by the 1-hour per-
incompatibility had a negative effect on the recovery of      centage of PLT recovery (PPR1hr), between ABO-identical
transfused PLTs in adults. Since then, this finding has been   and major-mismatched PLT transfusions; that is, from
confirmed by several studies. Lee and Schiffer11 found         group A donors to group O or B recipients, from group B
that ABO compatibility can affect the results of pooled       donors to group O or A recipients, and from group AB
random-donor PLT transfusions and that patients who           donors to group A, B, or O recipients, respectively. Major-
experience poor increments from ABO-mismatched PLTs           mismatched and bidirectionally mismatched transfusions
may benefit from ABO-compatible PLTs. Heal and col-            (i.e., both major- and minor-mismatched) were catego-
leagues12 reported that compared with ABO-unmatched           rized together. Secondary objectives were to compare the
PLTs, transfusion of ABO-identical PLTs is associated with    efficacy of ABO-identical PLT transfusions with major-
a significantly higher corrected count increment (CCI)         mismatched transfusions of group A subtypes A1 and A2 as
and with a twofold reduction of the risk to develop PLT       well as with minor-mismatched transfusions. Further-
refractoriness. While in these studies, pooled PLT products   more, side effects of PLT transfusions and data on the
were used and patients were randomly assigned to receive      production process of APCs were recorded prospectively.
either ABO-matched or ABO-unmatched transfusions,             The latter included information on the apheresis proce-
Jimenez and coworkers13 compared transfusion efficiency        dure, storage medium, storage time, volume, and gamma
of split apheresis products from the same donor in paired     irradiation.
recipients. If one recipient was ABO-identical and the
other was ABO-unmatched, mismatched transfusions
yielded one-third of the recovery of ABO-identical trans-     Patients
fusions. For the TRAP trial (Trial to Reduce Alloimmuni-      Between January 2004 and June 2006, all consecutive
zation to Platelets), Slichter and coworkers14 reported       patients with hematologic malignancies, solid tumors, or
significantly higher PLT increments after transfusion of       aplastic anemia requiring at least one PLT transfusion at
ABO-compatible PLTs. In lymphoma patients undergoing          the Division of Pediatric Hematology/Oncology of the
autologous marrow transplantation, leukoreduced ABO-          University Hospital Berne (Berne, Switzerland) were eli-
identical PLT transfusions were associated with reduced       gible for this trial. Exclusion criteria were refusal of study
morbidity.15 In cardiac surgery, ABO-mismatched PLT           participation, fever of 38.5°C or greater before transfu-
transfusions may be associated with a poor outcome.16         sion, clinically enlarged spleen, thrombosis, adverse
     All of these studies were performed in adult patients.   events requiring interruption of transfusion, and hemor-
In pediatric patients it has been more than 30 years since    rhage of WHO Grade 3 or greater. Before enrollment,
transfusion efficacy of ABO-mismatched PLTs has been           written informed consent was obtained from the parents
investigated. van Eys and coworkers17 reviewed the effects    and (as far as possible according to age) from the patient.
of 393 transfusions of pooled PLT products in pediatric       The study protocol was approved by the Government
cancer patients between 1973 and 1974. The authors con-       Ethics Committee of Berne, Switzerland. The study was
cluded that ABO matching had no effect on the success of      conducted in accordance with the principles of good clini-
a transfusion. Since this early study, production of PLT      cal practice.
concentrates has considerably improved. Within the past
decade, in many centers pooled PLT concentrates from
random units of whole blood have been replaced by             Preparation and delivery of PLTs
single-donor apheresis PLT concentrates (APCs).18,19          PLTs were obtained from healthy volunteer donors, either
Modern apheresis equipment typically achieves high PLT        by single- or by double-needle thrombocytapheresis using
yields with very low RBC and white blood cell contamina-      a cell separator (Amicus Crescendo, n = 105, Software
tion.20,21 The present prospective study was designed to      Version 2.51, Baxter, Deerfield, IL). Further APCs were
investigate the impact of providing either ABO-identical      produced by single-needle procedures using one of two
or out-of-group APCs to children with thrombocytopenia        different cell separators (Trima Accel, n = 277, Software
suffering from hematologic malignancies, solid tumors, or     Version 5.0, Gambro BCT, Lakewood, CO; or COBE
aplastic anemia.                                              Spectra, n = 18, Software Version 7.0, Gambro BCT). Aph-
                                                              eresis time was limited to 100 minutes. Depending on the
            PATIENTS AND METHODS                              yield, the apheresis product was split into units containing
                                                              at least 2.0 ¥ 1011 PLTs, corresponding to the minimum
Study design and objectives                                   content required by the standards of the Swiss Red Cross
In a prospective trial in children with thrombocytopenia,     at the time. APCs produced with the Amicus device were
we evaluated the influence of ABO blood group matching         suspended in 65 percent additive solution (AS; T-Sol, PAS
between PLT donor and recipient on posttransfusion PLT        II, Baxter) and 35 percent donor’s plasma according to the
increment. The primary objective was to detect differ-        manufacturer’s instructions, whereas PLTs derived from


22 TRANSFUSION Volume 49, January 2009
                                                                            TRANSFUSION EFFICACY OF MISMATCHED PLTs



the Trima and Spectra devices were suspended in 100              dose [1011/L]. Blood volume was determined according to
percent donor’s plasma. PLTs were stored at 22 2°C for a         Linderkamp and coworkers.24 Although determination of
maximum of 5 days on a flat-bed shaker with constant              the sample size by power analysis was based on the CCI1hr,
agitation until delivery for transfusion. Older products         the final analysis was based on PPR1hr rather than on CCI1hr
were delivered first, in line with the policy of our division     because of the inadequacy of the CCI1hr in infants and
of transfusion medicine to avoid expiration of APC prod-         small children; ergo only PPR1hr is shown throughout.
ucts. ABO-identical products were provided first; other-
wise minor- or major-mismatched PLTs were delivered at
the discretion of the staff. Wherever applicable no D+ PLTs      Determination of PLT count
were given to D– female recipients. Group O PLT donors
                                                                 PLT count in blood samples of patients was measured with
were screened for the presence of anti-A and anti-B
                                                                 a PLT analyzer (Cell Dyn 3500R, Abbott Laboratories,
hemolysins. If a titer of more than 4 was present, the
                                                                 Abbott Park, IL). In case of a PLT count of less than 30 ¥ 109
product was labeled accordingly and released for group O
                                                                 per L or an abnormal histogram pattern, manual counting
recipients only. When required, gamma irradiation of
                                                                 with a modified Neubauer counting chamber was
APCs was performed with a cesium irradiator (Gammacell
                                                                 performed.
3000 Elan, MDS Nordion, Ottawa, Canada) at doses of
                                                                      In each APC, after adhering to the preanalytic recom-
25 Gy.
                                                                 mendations of the apheresis device manufacturers, PLT
                                                                 count was determined with a hematology system (Advia
PLT transfusions                                                 120, Bayer, Leverkusen, Germany).

Most patients received prophylactic PLT transfusions,
with only a few receiving PLT transfusions for therapeutic
purposes. In children without purpura, excessive pete-           Determination of A antigen expression and A1/A2
chiae, widespread hematomas, epistaxis, mucosal bleed-           subgroup typing
ing, gastrointestinal bleeding, or genitourinary bleeding,       For major-mismatched transfusions from group A donors,
no PLTs were transfused, even when the PLT count was             A antigen expression on PLT surfaces was measured by
fewer than 10 ¥ 109 per L. As shown in Table 2, in defined        flow cytometry both in the APC and in the recipient before
clinical settings a PLT count of fewer than 10 ¥ 109 per L       and 1 hour after transfusion. For the first, we used a
triggered prophylactic transfusion. Bleeding episodes due        sample of the concentrate remaining in the tube of the
to thrombocytopenia were managed with PLTs until con-            transfusion set, and for the latter, PLT-rich plasma was
trolled. In all other situations, infants received 10 to 15 mL   obtained by centrifugation of blood samples. PLTs were
per kg body weight (BW) of the APC product. Children             diluted at a working concentration of 2 ¥ 107 PLTs per mL
less than 2 years old received half an APC product, and          with 20 mmol per L phosphate-buffered saline (PBS),
patients aged 2 years or more received a full APC product,       fixed in 1 percent paraformaldehyde (ratio 1:1), and incu-
independent of their BW. In line with our routine practice,      bated at room temperature for 30 minutes. The following
we recorded pulse rate and blood pressure before starting        monoclonal antibodies (MoAbs) were used: PLT gate was
the transfusion as well as every 3 minutes during transfu-       identified by staining PLTs with MoAb anti-CD61, directed
sion. Body temperature was measured before and after             against glycoprotein IIIa (Becton Dickinson, Franklin
transfusion. Patients were monitored for adverse events          Lakes, NJ). A antigen expression on PLT surface was
until 1 hour after the end of transfusion.                       assessed using anti-A reagent BRIC-145 (International
                                                                 Blood Group Reference Laboratory, Bristol, UK). Approxi-
                                                                 mately 106 PLTs were stained with the detecting antibodies
Efficacy measures: PPR1hr and 1-hour CCI (CCI1hr)                anti-CD61 and BRIC-145. At a working concentration of
Transfusion efficacy was determined by two surrogate              10 mg per mL, incubation was performed for 30 minutes
outcome measures. The CCI1hr allows to assess the efficacy        at 22°C. FITC-conjugated F(ab′)2 fragments of rabbit
of PLT transfusion accounting for the body surface area          anti-mouse immunoglobulin (Dako Diagnostics, Zug,
(BSA) and the number of transfused PLTs. It is calculated        Switzerland; final concentration 1.5 mg/mL) was added
as CCI1hr = BSA [m2] ¥ (posttransfusion count [109/              and incubated in the dark for an additional 30 minutes.
L] - pretransfusion count [109/L])/PLT dose [1011/L].22,23       The samples were then diluted at 1:20 with 20 mmol per L
Because in infants and children, blood volume is propor-         PBS and analyzed within 2 hours on a flow cytometer
tional to BW and is only suboptimally related to BSA,24 we       (FACScan, Becton Dickinson) equipped with a 15-mW air-
also used the BW-corrected measure, PPR1hr, as proposed          cooled argon laser. A total of 10,000 events per sample
by Hanson and Slichter25 and Davis and coworkers.26 It is        were gated and analyzed with computer software (Cell
calculated as PPR1hr [%] = (posttransfusion count [109/          Quest, Becton Dickinson). Results are reported as the per-
L] - pretransfusion count [109/L]) ¥ blood volume [L]/PLT        centage of PLTs positive for A antigen expression. Because


                                                                                Volume 49, January 2009    TRANSFUSION 23
JULMY ET AL.



donors are not screened for blood subgroups at our                 The Hodges-Lehmann method and the Wilcoxon U
center, we based the definition of subgroups A1 and A2 on      test cannot be extended to multivariate analyses. The
a publication of Cooling and colleagues.6 According to        British Committee for Standards in Haematology defines a
their data, no A antigen was detected by Western blot in A2   successful PLT transfusion as one with a PPR1hr of more
donors, while by flow cytometry the range of A antigen-        than 30 percent; thus, the outcome variable was dichoto-
positive PLTs varied between 4.3 and less than 1.0 percent.   mized into successful versus unsuccessful transfusions.
Being aware that some A2 donors will erroneously be           This binary outcome variable was then analyzed by logis-
allocated as group A1, we defined individuals with blood       tic regression stratified for patients. First, ABO-matching
group A presenting more than 1 percent A antigen-             status (identical vs. ABO major-mismatched transfusion
positive PLTs by flow cytometry to be of blood group A1        for the main study objective; other comparisons for sec-
and donors with 1 percent or less to be of subgroup A2.       ondary study objectives) was tested for potential associa-
                                                              tion with transfusion efficacy, that is, PPR1hr, by exact
                                                              univariate logistic regression. Second, asymptotic multi-
Fluorescent microscopy                                        variate logistic regression was performed in a similar
Cytocentrifuge PLT preparations were fixed with 4 percent      way to test if ABO-matching status was associated with
paraformaldehyde and stained with anti-A BRIC-145 and         transfusion efficacy independently from other patient-
with secondary antibody Cy-3 (Jackson ImmunoResearch          and APC-related variables. Exact multivariate logistic
Laboratories, Inc., West Grove, PA). Then, MoAb anti-         regression proved not feasible. The multivariate logistic
CD61 (Becton Dickinson) was used with a biotinylated          regression model started with all variables significantly
bridge antibody (Jackson ImmunoResearch), followed by         associated with transfusion efficacy in univariate analysis
anti-biotin Alexa 488 antibody (protein labeling kit          (p < 0.05). The backward variable selection procedure was
A-10235, Molecular Probes, Eugene, OR) to identify glyco-     applied until all variables remaining in the model were
protein IIIa on PLTs. Pictures were obtained by an imaging    significantly (p < 0.05) and independently associated with
system (Zeiss Axioplan 2, Zeiss, Zürich, Switzerland).        transfusion efficacy. ABO-matching status was then
                                                              included into this model.
                                                                   Baseline APC-related variables considered for multi-
Isohemagglutinin titer testing                                variate analysis were ABO and D blood group, storage
In many recipients, pretransfusion blood counts were          time, volume, PLT concentration, absolute PLT count,
determined by capillary blood sampling. Thus, isohemag-       apheresis procedure including apheresis device, duration
glutinin titers could only be analyzed for the patients       of thrombocytapheresis, processed blood volume, blood
undergoing venous blood sampling. With minor-                 flow, number of PLTs harvested per minute, yield per aph-
mismatched transfusions, isohemagglutinin titers were         eresis, weight before splitting, number of splits, and
determined in the donor plasma. For this purpose, residu-     gamma irradiation. Baseline patient variables considered
als of APCs remaining in the tube of the transfusion set      were ABO and D blood group, age, weight, and sex.
were transferred to test tubes to obtain plasma by cen-            Power analysis determined a sample size of 400 trans-
trifugation. Isohemagglutinin titers were determined          fusions for the primary objective (a = 5%, power 90%,
using a microtyping system (DiaMed-ID, DiaMed, Cressier       difference in the CCI1hr 5, estimated proportion of major-
sur Morat, Switzerland) according to the manufacturer’s       mismatched transfusions 25%, and sequential interim
instructions.                                                 analyses after 100, 200, and 300 transfusions). Two-sided
                                                              tests were used throughout, and p values below 0.05 were
                                                              considered significant. No correction for the multiple com-
Statistical analysis                                          parisons performed for secondary study objectives was
Because of nonnormally distributed data, medians,             applied. All exact analyses were performed with computer
ranges, and interquartile ranges (IQRs) were calculated for   software (StatXact 6 and LogXact 6, Cytel Software Corp.,
descriptive statistics, and nonparametric exact methods       Cambridge, MA); another software program (EaSt-2000,
were used wherever feasible for analytical statistics. For    Cytel Software Corp.) was used for sample size determina-
univariate main and secondary analyses, between-group         tion, performing of interim analyses, and correction of the
differences and their 95 percent confidence intervals          main-analysis p values for the interim analyses.
(CIs) were estimated using the exact Hodges-Lehmann
method. The corresponding p value was calculated using                               RESULTS
the exact Wilcoxon U test, stratified per patient. These
nonparametric methods correspond to parametric linear         Patient characteristics, PLT transfusions, and
mixed-effect (LME) modeling, which accounts for the cor-      indications
relation among multiple transfusions given to the same        During the study period, 52 children and adolescents
patient.                                                      received 528 PLT transfusions, of which 128 (24%) were


24 TRANSFUSION Volume 49, January 2009
                                                                                             TRANSFUSION EFFICACY OF MISMATCHED PLTs



excluded from analysis for the following reasons: fever                      given prophylactically and 14 (3.5%) therapeutically
of 38.5°C or greater before transfusion (n = 73), missing                    (Table 2).
pre- or posttransfusion PLT count (n = 16), clinically
enlarged spleen (n = 16), thrombosis (n = 11), APC
obtained from a foreign blood bank (n = 7), refusal of                       Constellations of ABO blood group matching of
study participation (n = 3), adverse events requiring                        donors and recipients
interruption of transfusion (n = 1), and hemorrhage of                       The 400 PLT transfusions included 282 (71%) ABO-
WHO Grade 3 or greater (n = 1). The eligible study                           identical, 76 (19%) major-mismatched, and 42 (11%)
population consisted of 50 children (29 girls, 21 boys)                      minor-mismatched transfusions, respectively (Table 3).
with a median age of 6.7 years at first transfusion (range,                   Among the 76 major-mismatched transfusions, there
0.2 to 16.1 years). They presented with thrombocytope-                       were 49 (12%) major-mismatched A1, 17 (4.3%) major-
nia due to the malignancy itself or the applied chemo-                       mismatched A2, and 8 (2.0%) major-mismatched transfu-
therapy or because of aplastic anemia (Table 1). The                         sions with other constellations (A1B, B). For 2 donors, 1
median number of APCs transfused per patient was 5                           with blood group A and 1 with blood group AB, A1/A2 sub-
(IQR, 3-10). Of 400 PLT transfusions, 386 (96.5%) were                       group typing by flow cytometry was not available.



     TABLE 1. Patient characteristics, number of PLT transfusions, and                             Interim analyses of the primary
           ABO blood group of patients and transfused APCs                                         study variable
                                                   Patients (%),           Transfusions (%),       The three planned interim analyses did
 Variables                                            n = 50                   n = 400
                                                                                                   not result in a proposal to stop the study
 Sex
   Male                                              21 (42%)                  189 (47%)
                                                                                                   early because of proven difference or
   Female                                            29 (58%)                  211 (53%)           proven futility. The standardized statis-
 Age (years)                                                                                       tics resulting from LME analysis of
   <1*                                                3 (6%)                    11 (3%)
     1 and <2*                                        5 (10%)                   38 (10%)
                                                                                                   CCI1hr in ABO matched versus major-
     2*                                              42 (84%)                  351 (88%)           mismatched transfusions were 0.81 for
 Diagnosis of patients                                                                             the first 100 transfusions (boundary to
   Acute lymphoblastic leukemia                      23   (46%)                141   (35%)
   Acute myelogenous leukemia                         6   (12%)                140   (35%)
                                                                                                   reject null hypothesis, 3.83; no bound-
   Lymphoma                                           1   (2%)                   1   (0%)          ary defined to reject alternative hypoth-
   Tumor of the central nervous system               11   (22%)                 58   (15%)         esis), 0.65 for 200 transfusions ( 2.80;
   Extracranial solid tumor                           8   (16%)                 38   (10%)
   Severe aplastic anemia                             1   (2%)                  22   (6%)
                                                                                                     0.40), and 1.64 for 300 transfusions
 ABO blood group                                                                                   ( 2.25; 1.37). At the time of study
   A                                                 22   (44%)                200   (50%)         design and interim analyses, CCI1hr to be
   B                                                  8   (16%)                 18   (5%)
   AB                                                 2   (4%)                   8   (2%)
                                                                                                   analyzed by LME was defined as the
   O                                                 18   (36%)                174   (44%)         principal outcome measure. At the stage
 * Patients less than 1 year received 10 to 15 mL per kg BW of the APC product, patients           of the final analysis, CCI1hr was replaced
   older than 1 and less than 2 years half an APC, and patients 2 years and older 1 APC.           by PPR1hr because of its improved



                     TABLE 2. Indications for transfusion and corresponding pretransfusion PLT counts
                                                                          Pretransfusion PLT count (¥109/L)
 Indications                                                               Median                   IQR                 Transfusions (%), n = 400
 Therapeutic use
   Minor bleeding (WHO Grade 2)                                               17                    6 to 37                      14 (4%)
 Prophylactic use
   Before RBC transfusion*                                                     9                    6   to   15                 138   (35%)
   Before invasive intervention†                                              20                   13   to   35                  91   (23%)
   Hospitalization because of severe neutropenia and fever*‡                   9                    7   to   15                  65   (16%)
   Prevention of further bleeding after major hemorrhage                      23                   19   to   40                  40   (10%)
   Before discharge from hospital*                                             9                    4   to   14                  38   (10%)
   Autologous stem cell transplantationठ                                    10                    8   to   14                  14   (4%)
 * A PLT count of fewer than 10 ¥ 109 per L triggered prophylactic transfusion.
 † Intramuscular injection, surgery, insertion of a central venous catheter, lumbar puncture. In case of circulating leukemic cells in the periph-
   eral blood before lumbar puncture, PLTs were transfused when the PLT count was fewer than 100 ¥ 109 per L.33
 ‡ Only transfusions given to patients with a body temperature of less than 38.5°C were considered eligible for this study.
 § Without fever a PLT count of fewer than 10 ¥ 109 per L and with fever a count of fewer than 20 ¥ 109 per L triggered prophylactic transfu-
   sion, respectively.



                                                                                                Volume 49, January 2009       TRANSFUSION 25
JULMY ET AL.



                                                                                                 from analysis, the failure rate
         TABLE 3. ABO blood group matching constellations (n = 400)                              of major-mismatched transfusions
   Blood group                                                                                   was even more striking (p = 0.002).
                                                   Recipient                                     However, minor-mismatched, plasma-
   Donor                A                  B                     AB                  O
                                                                                                 incompatible transfusions and identical
   A             129 (32%)            31 (7.8%)*‡            4 (1.0%)†           36 (9.0%)*§
     A1         No typing done        22 (5.5%)*‡         No typing done         27 (6.8%)*      transfusions were similarly successful
     A2         No typing done         9 (2.2%)*‡         No typing done          8 (2.0%)*      (p = 0.48).
   B                 2 (0.5%)*‡       14 (3.5%)              0                    2 (0.5%)*           In the multivariate analysis, pro-
   AB                1 (0.3%)*         3 (0.8%)*             3 (0.8%)             1 (0.3%)*§
     A1B             1 (0.3%)*         3 (0.8%)*             3 (0.8%)             0              duction of APCs according to the
     A2B             0                 0                     0                    0              Amicus procedure, which included
   O               18 (4.5%)†         19 (4.8%)†             1 (0.3%)†         136 (34%)         storage in PLT AS (p < 0.001), a longer
   Total         150 (38%)            67 (17%)               8 (2%)            175 (44%)         storage     time   before    transfusion
   * Major-mismatched transfusions.                                                              (p = 0.003), and a higher PLT yield per
   † Minor-mismatched transfusions.
   ‡ Bidirectionally mismatched transfusions (i.e., both major- and minor-mismatched).
                                                                                                 apheresis (p < 0.001) were significantly
   § For one donor with blood group A and one donor with blood group AB, A1/A2 subgroup          associated with a higher number of
     typing was not available.                                                                   unsuccessful transfusions, whereas a
                                                                                                 higher PLT count per APC (p < 0.001)
                                                                                                 and an increasing BW of the recipient
accuracy in infants and small children25,26 and exact logis-                 (p = 0.003) had a positive impact (Table 5). In this context,
tic regression replaced parametric LME. Interim analyses                     we have recently reported on the effects of these variables
using exact logistic regression on PPR1hr, however, would                    on the efficacy of transfused PLTs.27
have resulted in the same decisions, with standardized
statistics of 0.35, 1.15, and 1.75 after 100, 200, and 300
transfusions, respectively, in post hoc calculations.                        Fate of transfused A antigen-positive PLTs
                                                                             In 32 major-mismatched transfusions from group A1
                                                                             donors to group O (n = 18) or group B (n = 14) recipients,
PLT transfusion efficacy                                                     the percentage of A antigen-positive PLTs was determined
Table 4 shows the transfusion efficacy depending on ABO                       by flow cytometry in the APC and in the recipient before
matching. The median PPR1hr of all transfusions was 31                       and 1 hour after transfusion. In the recipient, there were
percent. Univariate analysis showed PPR1hr for 76 major-                     no A antigen-positive PLTs before transfusion (data not
mismatched transfusions to be significantly inferior to                       shown). Figures 1A and 1B show that in the majority of
that for 282 ABO-identical transfusions (median, 21% vs.                     group O and B recipients, no A antigen-positive PLTs were
32%; p = 0.034); notably for major-mismatched A1 PLTs                        detectable in the circulation 1 hour after transfusion. In
the median PPR1hr was 44 percent lower compared to                           contrast, after ABO-identical PLT transfusions from group
ABO-identical PLTs (median, 18% vs. 32%; p = 0.007). Con-                    A1 donors to group A2 recipients, whose RBCs but not PLTs
cerning transfusion success or failure, major-mismatched                     express A antigen, the majority of transfused A antigen-
transfusions were significantly more often unsuccessful                       positive PLTs remained detectable in the circulation
than ABO-identical transfusions (p = 0.033), especially                      (Fig. 1C). Figure 2 depicts flow-cytometric histograms of
many major-mismatched transfusions from subgroup A1                          four typical PLT transfusions with different ABO constel-
donors failed (p = 0.002). Major-mismatched A2 PLTs                          lations. The percentages of A antigen-positive PLTs in the
were as successful as ABO-identical ones (p = 1.00). No                      APC and blood of the recipient before and after transfu-
significant difference between ABO-identical and ABO                          sion are indicated. It is noteworthy that A antigen-positive
nonidentical transfusions (i.e., the sum of major- and                       PLTs, which remained detectable 1 hour after transfusion,
minor-mismatched transfusions) was seen (p = 0.22;                           expressed low amounts of A antigen only (Figs. 2A and 2B,
Table 4).                                                                    Row 3). In Fig. 3, using the MoAb anti-CD61 for identifica-
      Multivariate analysis fully confirmed these results                     tion of PLTs and anti-A BRIC-145 for expression of A
(Table 5). Major-mismatched transfusions were signifi-                        antigen, depletion of transfused A antigen-positive PLTs
cantly more often unsuccessful than ABO-identical trans-                     from the circulation of a blood group O recipient is visu-
fusions (p = 0.005). As shown in Table 6, subgroup analysis                  alized at a single-cell level by dual-color fluorescent
revealed that PLTs from donors with ABO subgroup A2                          microscopy. Regression analysis showed that for group A
given to group O or B recipients, although major-                            major-mismatched transfusions, there was a significant
mismatched transfusions, by definition, were just as suc-                     negative correlation (p = 0.002) between the percentage of
cessful as ABO-identical PLTs (p = 0.90). Therefore, by                      A antigen-positive PLTs in the APC and the PPR1hr; that is,
reanalyzing ABO-identical versus major-mismatched                            the more PLTs expressed A antigen, the lower the PPR1hr
transfusions after excluding the 17 A2 PLT products                          (Fig. 4).

26 TRANSFUSION Volume 49, January 2009
                                                                                                                                                                                                                                                                                                                                      TRANSFUSION EFFICACY OF MISMATCHED PLTs



                                                                                                                                                                                                                                                                                                                                To substantiate the hypothesis that in group O or B




                                                                                                                        p Value



                                                                                                                                           0.033‡
                                                                                                                                                                                                                                                                                                                           recipients, the transfused A antigen-positive PLTs are




                                                                                                                                           0.002

                                                                                                                                           0.007
                                                                                                                                           1.00

                                                                                                                                           0.59
                                                                                                                                           0.22
                                                                                                                                                                                                                                                                                                                           rapidly cleared from the circulation in vivo, we performed
                                                                                                                                                                                                                                                                                                                           in vitro experiments (n = 3; Fig. 5). Blood treated with eth-
                                                                                                                                                                                                                                                                                                                           ylenediaminetetraacetic acid (EDTA) was obtained from



                                                                                                                                        1.65 to 18.49
                                                                                                                                        1.18 to 6.44

                                                                                                                                        0.14 to 4.21
                                                                                                                                        1.34 to 9.72
                                                                                                                                        0.26 to 1.89
                                                                                                                                        0.81 to 2.81
                                                                                                                                                                                                                                                                                                                           recipients with blood group O before PLT transfusion. The
                                                                                                                                         Reference
                                                                                                               95% CI


                                                                                                                                                                                                                                                                                                                           patients were transfused with an A1 major-mismatched
                                                                                                              30%




                                                                                                                                                                                                                                                                                                                           APCs. Thereafter, transfused PLTs (100 mL) remaining in the
                                                                                                                                                                                                                                                                                                                           transfusion set were added to the recipient’s blood sample.
TABLE 4. Univariate analysis of PLT transfusion efficacy and transfusion failure* depending on ABO matching
                                                                                                               PPR1hr




                                                                                                                                                                                                                                                                                                                           One hour later, blood samples from both the patients and


                                                                                                                                                                 According to the British Committee for Standards in Haematology an unsuccessful PLT transfusion was defined as one with a PPR1hr of 30 percent or less.2
                                                                                                                                                                                                                                                                                                                           the in vitro prepared samples were analyzed in parallel by
                                                                                                                                           2.67
                                                                                                                                           4.98
                                                                                                                                           0.78
                                                                                                                                           3.41
                                                                                                                                           0.71
                                                                                                                                           1.49
                                                                                                              OR




                                                                                                                                                                                                                                                                                                                           flow cytometry. In the recipient’s blood, no A antigen-
                                                                                                                                                                                                                                                                                                                           positive PLTs were detected, whereas in vitro similar per-
                                                                                                                        Number (%)




                                                                                                                                                                                                                                                                                                                           centages of A antigen-positive PLTs that were previously
                                                                                                                                     (47%)
                                                                                                                                     (44%)
                                                                                                                                     (62%)
                                                                                                                                     (71%)
                                                                                                                                     (35%)
                                                                                                                                     (68%)
                                                                                                                                     (40%)
                                                                                                                                     (54%)




                                                                                                                                                                                                                                                                                                                           measured in the transfused APCs were recovered.
                                                                                                                                     187
                                                                                                                                     123
                                                                                                                                      47
                                                                                                                                      35
                                                                                                                                       6
                                                                                                                                      39
                                                                                                                                      17
                                                                                                                                      64




                                                                                                                                                                                                                                                                                                                           Safety review and isohemagglutinin titers
                                                                                                                        p Value




                                                                                                                                                                                                                                                                                                                           During the whole study period in which the transfusion of
                                                                                                                                           0.034†
                                                                                                                                           0.005

                                                                                                                                           0.007
                                                                                                                                           0.78

                                                                                                                                           0.49
                                                                                                                                           0.22




                                                                                                                                                                                                                                                                                                                           528 APCs was available for safety review, no clinically
                                                                                                                                                                                                                                                                                                                           detectable hemolytic transfusion reaction was observed;
                                                                                                                                                                                                                                                                                                                           however, we did not test for subclinical manifestations of
                                                                                                                                        -12.5 to -1.6
                                                                                                                                        -15.9 to -4.5

                                                                                                                                        -15.8 to -4.2
                                                                                                                                         -5.4 to 15.5

                                                                                                                                         -4.1 to 10.1



                                                                                                                                                                 p Value adjusted from a calculated p value of 0.017 for the interim analyses performed for this primary outcome.
                                                                                                                                                                 p Value adjusted from a calculated p value of 0.016 for the interim analyses performed for this primary outcome.




                                                                                                                                                                                                                                                                                                                           hemolysis. Notably, only 1 (0.2%) of 528 transfusions had
                                                                                                                                         References




                                                                                                                                         -8.2 to 1.2
                                                                                                                        95% CI




                                                                                                                                                                                                                                                                                                                           to be interrupted due to a major transfusion reaction
                                                                                                                                                                                                                                                                                                                           (angioedema). Minor transfusion reactions were also rare
                                                                                                                                                                                                                                                                                                                           (6/528; 1.1%). In 32 plasma-incompatible transfusions,
                                                                                                                                                                                                                                                                                                                           isohemagglutinin titers were determined in the APCs
                                                                                                                                                                                                                                                                                                                           revealing no titer greater than 32. In the recipients, titers
                                                                                                              Estimated difference
                                                                                                                     PPR1hr (%)




                                                                                                                                                                                                                                                                                                                           were determined before PLT transfusion in 228 cases
                                                                                                                                                                                                                                                                                                                           revealing low medians of anti-A and anti-B isohemagglu-
                                                                                                                                            -7.2
                                                                                                                                           -10.6
                                                                                                                                             5.1
                                                                                                                                           -10.3
                                                                                                                                             2.9
                                                                                                                                            -3.9




                                                                                                                                                                                                                                                                                                                           tinins (Table 7). Statistically, no association between
                                                                                                                                                                                                                                                                                                                           transfusion efficacy and the recipient’s isohemagglutinin
                                                                                                                                                                                                                                                                                                                           titers were detected (data not shown). It is noteworthy that
                                                                                                                                                                                                                                                                                                                           during the study period no patient became PLT refractory,
                                                                                                                                                                                                                                                                                                                           shown by an adequate PPR1hr after subsequent transfu-
                                                                                                                                     45
                                                                                                                                     44
                                                                                                                                     40
                                                                                                                                     34
                                                                                                                                     52
                                                                                                                                     37
                                                                                                                                     52
                                                                                                                                     45




                                                                                                                                                                                                                                                                                                                           sions, and therefore HLA/HPA-matched PLTs were never
                                                                                                                        IQR
                                                                                                                                     to
                                                                                                                                     to
                                                                                                                                     to
                                                                                                                                     to
                                                                                                                                     to
                                                                                                                                     to
                                                                                                                                     to
                                                                                                                                     to




                                                                                                                                                                                                                                                                                                                           required.
                                                                                                                                     17
                                                                                                                                     19
                                                                                                                                     12
                                                                                                                                     13
                                                                                                                                     17
                                                                                                                                     10
                                                                                                                                     16
                                                                                                                                     14




                                                                                                                                                                 The sum of major- and minor-mismatched transfusions.




                                                                                                                                                                                                                                                                                                                                                DISCUSSION
                                                                                                                        Median
                                                                                                                                     31
                                                                                                                                     32
                                                                                                                                     21
                                                                                                                                     18
                                                                                                                                     36
                                                                                                                                     18
                                                                                                                                     34
                                                                                                                                     26




                                                                                                                                                                                                                                                                                                                           PLT transfusions are administered to patients with throm-
                                                                                                                                                                                                                                                                                                                           bocytopenia to prevent or stop hemorrhage. Because
                                                                                                                                                                                                                                                                                                                           intensive treatment regimens, including allogeneic and
                                                                                                                        Number
                                                                                                                                     400
                                                                                                                                     282
                                                                                                                                      76
                                                                                                                                      49
                                                                                                                                      17
                                                                                                                                      57
                                                                                                                                      42
                                                                                                                                     118




                                                                                                                                                                                                                                                                                                                           autologous stem cell transplantation, are increasingly
                                                                                                                                                                                                                                                                                                                           applied, hematology/oncology patients are currently
                                                                                                                                                                                                                                                                                                                           among the largest groups receiving PLT transfusions.19,28
                                                                                                                                                                                                                                                                                                                           In this context, the clinical significance of ABO compat-
                                                                                                                                       Major-mismatched non-A2




                                                                                                                                                                                                                                                                                                                           ibility in PLT transfusion has been a matter of debate since
                                                                                                                                     ABO major-mismatched



                                                                                                                                     ABO minor-mismatched
                                                                                                                                       Major-mismatched A1
                                                                                                                                       Major-mismatched A2




                                                                                                                                                                                                                                                                                                                           the early studies of Aster,10 more than 40 years ago. He and
                                                                                                                                     ABO non identical§




                                                                                                                                                                                                                                                                                                                           others have recognized that ABO-incompatible PLTs
                                                                                                              PLT transfusions




                                                                                                                                                                                                                                                                                                                           may be associated with decreased PLT increments after
                                                                                                                                     ABO-identical




                                                                                                                                                                                                                                                                                                                           transfusion.11-14 However, not only PLT-incompatible
                                                                                                                                                                                                                                                                                                                           transfusions, that is, major-mismatched transfusions,
                                                                                                              Type
                                                                                                                                     Total




                                                                                                                                                                                                                                                                                                                           but also plasma-incompatible transfusions, that is, minor-
                                                                                                                                                                 †
                                                                                                                                                                 ‡
                                                                                                                                                                 §
                                                                                                                                                                 *




                                                                                                                                                                                                                                                                                                                           mismatched transfusions, have attracted attention,


                                                                                                                                                                                                                                                                                                                                          Volume 49, January 2009   TRANSFUSION 27
JULMY ET AL.



                                                                                             because they have been linked to acute
             TABLE 5. Multivariate logistic regression of factors affecting                  hemolytic        transfusion   reactions,
                       transfusion failure* (primary objective)
                                                                                             venoocclusive disease, and increased
                                                             PPR1hr 30%
                                                                                             morbidity in allogeneic transplant
  Variable                                      OR             95% CI            p Value
                                                                                             recipients.9,29,30
  ABO matching–related
    ABO major-mismatched vs. -identical        3.97          1.52 to 10.39        0.005           The majority of studies have been
  Product-related                                                                            performed in adult patients, and PLT
    Apheresis and storage procedure:           7.82          3.35 to 18.25       <0.001
                                                                                             transfusion in children is poorly investi-
    Amicus vs. others
    Storage time of APC (per day)              1.46         1.13 to 1.87          0.003      gated. In addition, in the majority of
    Absolute PLT count of APC (per 1011)       0.090       0.023 to 0.354        <0.001      older reports, transfusion of pooled PLT
    Yield of apheresis (per 1011 PLTs)         1.37         1.16 to 1.63         <0.001
                                                                                             concentrates from random units of
  Recipient-related
    Weight of recipient (per kg)               0.83          0.74 to 0.94         0.002      whole blood has been studied, but these
  * According to the British Committee for Standards in Haematology, unsuccessful PLT        PLT products have been widely replaced
    transfusion is defined as one with a PPR1hr of 30 percent or less.2                       by APCs within the past decade.18,19 With
                                                                                             modern apheresis equipment, a high
                                                                                             PLT yield can be obtained allowing the
                                                                                             production of two, three, or even more
                                                                                             APCs from a single donation.20,21
         TABLE 6. Multivariate logistic regression of ABO-matching                                The aim of this prospective study
     constellations affecting transfusion failure* (secondary objectives)†                   was to investigate transfusion efficacy
                                                              PPR1hr 30%                     and transfusion success of APCs in
  Variable                                       OR            95% CI            p Value
                                                                                             children with thrombocytopenia. The
  ABO matching–related
   Major-mismatched A1 vs. identical            9.30        2.53   to   34.24    <0.001      primary objective was to test the
   Major-mismatched A2 vs. identical            1.13        0.16   to   7.88      0.90       hypothesis that transfusion efficacy of
   Major-mismatched non A2 vs. identical        5.81        1.94   to   17.38     0.002      ABO major-mismatched PLTs is signifi-
   ABO minor-mismatched vs. identical           0.67        0.22   to   2.02      0.48
   ABO nonidentical vs. identical               1.69        0.83   to   3.45      0.15       cantly inferior to that of ABO blood
  * According to the British Committee for Standards in Haematology, unsuccessful PLT        group–identical PLTs. A randomized
    transfusion is defined as one with a PPR1hr of 30 percent or less.2                       study design would have increased the
  † Each subgroup analysis was adjusted for the corresponding patient- and product-          power of our study. However, in view of
    related variables (data not shown).
                                                                                             the preceding studies in adults,10-13,15,16
                                                                                             we considered such a design incompat-
                                                                                             ible with good clinical practice in this
                                                                                             vulnerable pediatric population. There-
                                                                                             fore, power calculation was based on
                                                                                             a retrospective review of the ABO-
                                                                                             matching status of 50 APCs that had
                                                                                             been delivered between May 2003 and
                                                                                             October 2003, in line with the policy of
                                                                                             our division of transfusion medicine,
                                                                                             which remained unchanged during the
                                                                                             study period. Since PLT transfusion effi-
                                                                                             cacy not only depends on ABO match-
                                                                                             ing, patient- and APC-related factors
                                                                                             were also assessed prospectively.
                                                                                                  While planning the study, we con-
                                                                                             sidered basing the primary study objec-
                                                                                             tive on a robust clinical endpoint, such
                                                                                             as cessation of bleeding. However, a
                                                                                             retrospective review revealed that in
Fig. 1. Percentage of A antigen-expressing PLTs in APCs and blood of recipients 1            our pediatric hematology/oncology pa-
hour after transfusion. Before transfusion, no A antigen-positive PLTs were detected         tients, the vast majority of PLT transfu-
in the recipients (data not shown). (A) Major-mismatched transfusions of group A1            sions were given prophylactically rather
PLTs to group O recipients (n = 18), (B) to group B recipients (n = 14), and (C) identi-     than therapeutically,28,31 and the fre-
cal transfusions of A1 PLTs to group A2 recipients (n = 3; serving as in vivo control). In   quency of major and minor bleeding
each panel, the medians are shown by bars.                                                   episodes was very low. Therefore, we


28 TRANSFUSION Volume 49, January 2009
TRANSFUSION EFFICACY OF MISMATCHED PLTs




   Volume 49, January 2009   TRANSFUSION 29
JULMY ET AL.



Fig. 2. Percentage of A antigen-positive PLTs in the APCs and blood of recipients before and 1 hour after major-mismatched trans-
fusion (A-C) or identical transfusion (D). (A-D) PLTs were stained with BRIC-145 and labeled with FITC to identify the blood group
A antigen. (A) Group O recipient transfused with group A1 PLTs, (B) group B recipient transfused with group A1 PLTs, (C) group O
recipient transfused with group A2 PLTs, and (D) group A2 recipient transfused with group A1 PLTs. Columns 1, 2, and 3 show respec-
tive histograms of the recipient’s PLTs before transfusion, of the APCs, and of the recipient’s PLTs 1 hour after transfusion. Horizon-
tal brackets indicate A antigen-positive PLTs. PLTs left of brackets are considered to be A antigen-negative. In each histogram the
percentage of A antigen-positive PLTs is inserted as well as the particular ABO blood group of the recipient and/or donor.
MFI = mean fluorescence intensity.




Fig. 3. Fluorescent microscopy of A antigen-positive PLTs in an APC and in the blood of a blood group O recipient 1 hour after
major-mismatched transfusion. Fixed PLTs were stained with anti-A (red) and anti-CD61 (green) as described under Materials and
Methods. Column A = PLTs of an APC obtained from a donor with blood group A1. In this APC, 41 percent of the PLTs expressed A
antigen as measured by flow cytometry. Column B = PLTs from the recipient 1 hour after transfusion of the APC shown in Column
A. Row 1 = PLTs expressing A antigen (red); Row 2 = PLTs identified with anti-CD61 (green); Row 3 = fusion dual-color picture
depicting A antigen-positive PLTs in yellow whereas A antigen-negative PLTs remain green. After transfusion, confirmed by flow
cytometry, no (0%) A antigen-positive PLTs remained in the circulation of the recipient.

chose to base our statistical endpoints on CCI1hr and PPR1hr              Our results demonstrate that transfusion efficacy and
as surrogate parameters for PLT transfusion efficacy. CCI1hr           transfusion success, the latter defined as PPR1hr of more
accounts for BSA and is well established in adults,22,23              than 30 percent, of major-mismatched PLTs are signifi-
whereas PPR1hr accounts for BW and is reported to be more             cantly inferior to those of ABO-identical PLTs, whereas
appropriate in children, particularly in infants and tod-             efficacy and success of minor-mismatched transfusions
dlers.25,26 Because of the latter the final analysis was based         are not different from those of identical transfusions. It
on PPR1hr.                                                            is noteworthy that comparison of transfusion success


30 TRANSFUSION Volume 49, January 2009
                                                                                  TRANSFUSION EFFICACY OF MISMATCHED PLTs



of nonidentical (i.e., the sum of minor- and major-                    efficacy between ABO-identical and major-mismatched
mismatched) PLTs with that of ABO-identical PLTs did not               PLTs could have been missed.17
reveal any significant difference (Table 6). A limitation of                 In accordance with earlier reports,5,6 we observed a
some older studies is that nonidentical transfusions were              dramatic diversity in the percentages of PLTs expressing A
not categorized into minor- (plasma-incompatible) and                  antigen among A1 donors (median, 40%; range, 3%-80%).
major- (PLT-incompatible) mismatched transfusions,                     High A antigen expression may be the main pathophysi-
bearing the risk that significant differences in transfusion            ologic mechanism explaining the rapid clearance of these
                                                                       PLTs from circulation after transfusion into group O or B
                                                                       recipients. This notion appears to be supported by our
                                                                       observation that the percentage of A antigen-expressing
                                                                       PLTs and PPR1hr were inversely related; that is, the higher
                                                                       the percentage of A antigen-expressing PLTs, the lower the
                                                                       PPR1hr (Fig. 4). Moreover, our experiments showed that
                                                                       after in vitro incubation of A antigen-positive PLTs in
                                                                       group O blood samples, the percentages of positive PLTs
                                                                       did little change, while in vivo, 1 hour after transfusion, A
                                                                       antigen-positive PLTs were no longer detected in the
                                                                       blood of the recipients (Fig. 5). Therefore, we hypothesize
                                                                       that any PLT increment after transfusing PLTs from group
                                                                       A1 donors into group O or B recipients is due to PLTs
                                                                       expressing no or low levels of A antigen. Because median
                                                                       anti-A titers in the plasma of blood group O recipients was
Fig. 4. Linear regression of PPR1hr and percentage of A                higher (8) than in plasma of group B recipients (2; Table 7),
antigen-positive PLTs in group A major-mismatched transfu-             we speculate that this may explain the slightly better sur-
sions. The solid line represents the linear regression line, and       vival of transfused A1 PLTs in group B recipients (Fig. 1).
the dashed line indicates the border between a successful              Furthermore, our data confirmed the conclusion of
(>30%) and an unsuccessful PPR1hr ( 30%) as defined by the              others6 that A2 PLTs can be considered group O compat-
British Committee for Standards in Haematology.2                       ible. With 8 percent of the Swiss population having blood




Fig. 5. Comparison of A antigen expression in vivo and in vitro in a major-mismatched transfusion constellation. A antigen-positive
donor’s PLTs (100 mL) were added in vitro to 2 mL EDTA blood obtained from a recipient with blood group O before transfusion and
incubated for 1 hour. Histograms are explained in the legend to Fig. 2. (A) A antigen expression in the APC, (B) in the recipient
before and (C) 1 hour after transfusion, and (D) in the sample prepared in vitro. In each histogram the percentage of A antigen-
positive PLTs is inserted.



                   TABLE 7. Isohemagglutinin titers in APCs and plasma of recipients before transfusion
                        Plasma-incompatible PLT concentrates (n = 32)                           Recipients (n = 228)
                               Anti-A                         Anti-B                      Anti-A                          Anti-B
  Blood group      Number      Median      Range      Median         Range    Number      Median       Range        Median       Range
  O                  16           8         1-32          4           1-16     108           8         0-128          4          0-128
  A                  15                                   4           1-32      86                                    4          0-64
  B                   1           4                                             34           2         0-32



                                                                                       Volume 49, January 2009    TRANSFUSION 31
JULMY ET AL.



group A2,32 routine A1/A2 subtyping of group A donors                 manuscript. We also wish to thank all patients and their families
would expand the available inventory of compatible PLTs               for having consented to participate in this study.
for group O recipients. It remains to be shown if PLTs from
blood group A1 donors with a low expresser phenotype
                                                                                            REFERENCES
would produce a sufficient PLT increase in group O or B
recipients.                                                            1. American Association of Blood Banks. Technical manual.
     Whereas ABO matching clearly influenced transfu-                      15th ed. Bethesda (MD): American Association of Blood
sion success or failure, further factors revealed to be sig-              Banks; 2005.
nificantly associated with transfusion efficacy. Whereas                 2. British Committee for Standards in Haematology, Blood
the apheresis procedure including storage conditions, the                 Transfusion Task Force (Chairman P Kelsey). Guidelines for
storage time, and the PLT yield per apheresis procedure                    the use of platelet transfusions. Br J Haematol 2003;122:10-
had an unfavorable impact, a higher PLT count per APC                      23.
and increasing BW of the recipient favored successful                  3. Julmy F, Achermann F, Schulzki T, Carrel T, Nydegger U.
transfusions (Table 5). Therefore, separate from this study,              PLTs of blood group A1 donors express increased surface A
we have recently reported on the effects of these variables               antigen owing to apheresis and prolonged storage. Trans-
on the transfusion efficacy of PLT products.27                             fusion 2003;43:1378-85.
     Safety review of transfusions confirmed the good                   4. Ogasawara K, Ueki J, Takenaka M, Furihata K. Study on the
tolerability of PLT transfusions. No clinically detectable                 expression of ABH antigens on platelets. Blood 1993;82:
hemolytic reactions were observed in 528 recorded PLT                     993-9.
transfusions disregarding the matching status, and there               5. Curtis BR, Edwards JT, Hessner MJ, Klein JP, Aster RH.
was only 1 (0.2%) transfusion that had to be interrupted                   Blood group A and B antigens are strongly expressed
due to a major transfusion reaction. Each group O PLT                      on platelets of some individuals. Blood 2000;96:
donor was routinely screened for the presence of anti-A                   1574-81.
and anti-B hemolysins. If a titer of greater than 4 was                6. Cooling LL, Kelly K, Barton J, Hwang D, Koerner TA, Olson
present, according to the standards of the Swiss Red                       JD. Determinants of ABH expression on human blood
Cross, the product was labeled accordingly and released                   platelets. Blood 2005;105:3356-64.
for group O recipients only. The latter fact may account               7. Duguid JK, Minards J, Bolton-Maggs PH. Lesson of the
for absence of hemolysis after plasma-incompatible                        week: incompatible plasma transfusions and haemolysis in
transfusions. Furthermore, no patient became PLT                          children. BMJ 1999;318:176-7.
refractory, and patients’ anti-A and anti-B isohemagglu-               8. Larsson LG, Welsh VJ, Ladd DJ. Acute intravascular
tinins remained low despite having received major-                        hemolysis secondary to out-of-group platelet transfusion.
mismatched PLT transfusions, in many cases more than                       Transfusion 2000;40:902-6.
one.                                                                   9. Herman JH, King KE. Apheresis platelet transfusions: does
     In conclusion, major-mismatched PLT transfusions                     ABO matter? Transfusion 2004;44:802-4.
were significantly less successful than ABO-identical                  10. Aster RH. Effect of anticoagulant and ABO incompatibility
transfusions. In children requiring regular and continued                 on recovery of transfused human platelets. Blood 1965;26:
PLT support, an ABO-compatible transfusion strategy                       732-43.
should be the first choice. In this context, A2 PLTs are               11. Lee EJ, Schiffer CA. ABO compatibility can influence the
equivalent to group O PLTs. For this finding to be of                      results of platelet transfusion. Results of a randomized
practical value, PLT concentrate suppliers would have to                  trial. Transfusion 1989;29:384-9.
provide A1/A2 subgroup typing of group A PLT donors. In               12. Heal JM, Rowe JM, McMican A, Masel D, Finke C,
this study, transfusion of plasma-incompatible PLTs was                   Blumberg N. The role of ABO matching in platelet
as successful as that of identical PLTs, although an inher-               transfusion. Eur J Haematol 1993;50:110-7.
ent risk for hemolytic transfusion reactions will remain.             13. Jimenez TM, Patel SB, Pineda AA, Tefferi A, Owen WG.
                                                                          Factors that influence platelet recovery after transfusion:
                                                                          resolving donor quality from ABO compatibility. Transfu-
ACKNOWLEDGMENTS
                                                                          sion 2003;43:328-34.
The authors thank all members of the medical, nursing, and labo-      14. Slichter SJ, Davis K, Enright H, Braine H, Gernsheimer T,
ratory staff of the Division of Pediatric Hematology/Oncology of          Kao KJ, Kickler T, Lee E, McFarland J, McCullough J, Rodey
the University Children’s Hospital Berne and the Division of              G, Schiffer CA, Woodson R. Factors affecting posttransfu-
Transfusion Medicine of the Department of Hematology, Univer-             sion platelet increments, platelet refractoriness, and plate-
sity Hospital Berne. We are especially indebted to the nurses of          let transfusion intervals in thrombocytopenic patients.
the apheresis unit. We are grateful to Jakob Zbaeren for his excel-       Blood 2005;105:4106-14.
lent technical assistance in fluorescent microscopy and to Dr          15. Heal JM, Blumberg N, Kirkley SA, DiPersio JF, Rapoport AP,
Silvia M. Rogers (MediWrite, Basel, Switzerland) for reviewing the        Rowe JM. Leukocyte-reduced transfusions of ABO-identical


32 TRANSFUSION Volume 49, January 2009
                                                                               TRANSFUSION EFFICACY OF MISMATCHED PLTs



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                                                                                    Volume 49, January 2009    TRANSFUSION 33

				
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