Laboratory Performance in Neonatal Bilirubin Testing Using Commutable Specimens A Progress Report o by ProQuest


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									    Laboratory Performance in Neonatal Bilirubin Testing
               Using Commutable Specimens
                A Progress Report on a College of American Pathologists Study
                                Stanley F. Lo, PhD; Bernadine Jendrzejczak, BA; Basil T. Doumas, PhD

● Context.—In 2003 the Chemistry Resource Committee of                  variation for the 4 major instrument groups (Dimension,
the College of American Pathologists introduced a com-                  Olympus, Synchron, and Vitros), which report 65% of all
mutable specimen in the Neonatal Bilirubin Surveys. This                results, varied from 2% to 3%. College of American Pa-
specimen was intended to help evaluate all bilirubin meth-              thologists All Data mean bilirubin values were within 0.46
ods.                                                                    mg/dL (7.8 mol/L) of the reference method mean in
   Objective.—To evaluate the effect of commutable spec-                2003; in subsequent years these differences became larger,
imens on the performance of selected clinical analyzers in              peaking at 1.87 mg/dL (32 mol/L) in 2005.
measuring neonatal bilirubin from 2003 through 2006.                       Conclusions.—The large systematic error of bilirubin
   Design.—A human serum–based specimen enriched                        measurements is due primarily to failure of instrument
with unconjugated bilirubin in human serum has been in-                 manufacturers to produce reliable bilirubin calibrators.
cluded since 2003 in the Neonatal Bilirubin Surveys. The                Primary calibrators should consist of human serum en-
bilirubin values of these specimens were determined by the              riched with unconjugated bilirubin. Bilirubin values must
reference method and used to evaluate results reported by               be assigned by the reference method, the performance and
various chemistry analyzers.                                            robustness of which are reported in this article. Secondary
   Results.—Coefficients of variation for College of Amer-               calibrators distributed to users must be traceable to pri-
ican Pathologists All Data ranged from 4.9% to 6.2% for                 mary calibrators.
the Neonatal Bilirubin Survey. However, coefficients of                     (Arch Pathol Lab Med. 2008;132:1781–1785)

I  n 2003, the Chemistry Resource Committee of the Col-
    lege of American Pathologists (CAP), acting on a report
regarding inaccuracies in the measurement of bilirubin in
                                                                        mg/dL (428 mol/L) cannot be reduced by photothera-
                                                                        py.2 Because this is considered a critical bilirubin value,
                                                                        the CAP Chemistry Resource Committee decided to adjust
clinical laboratories,1 introduced a new specimen in the                the bilirubin level in the human serum–based specimen
Neonatal Bilirubin Surveys (NB-Surveys). This specimen,                 near 25 mg/dL (428 mol/L).
human serum enriched with unconjugated bilirubin, was                      Results from the 2003 human serum–based specimen
expected to be commutable (free of matrix effects) because              (NB-02) were very encouraging. The grand mean value for
it closely resembles specimens drawn from healthy neo-                  CAP All Data was only 2.4% higher than the reference
nates. Properly calibrated clinical analyzers were expected             method mean and the coefficient of variation (CV) % of
to be accurate, providing total bilirubin (TBIL) values close           5.7.
to those obtained by the reference method. The noncom-                     This communication is a progress report on the perfor-
mutable or conventional NB-Survey specimens consisted                   mance of laboratories participating in the NB-Surveys for
of unconjugated bilirubin and ditaurobilirubin in bovine                the years 2004 through 2006. The practice of including the
serum.1                                                                 special, commutable NB-Survey specimen in the Chemis-
   A guideline issued by the American Academy of Pedi-                  try Survey (C-Survey), as specimen C-96 or C-97, contin-
atrics recommended a blood exchange transfusion for in-                 ued until the end of year 2006.
fants older than 48 hours when bilirubin levels near 25
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