Docstoc

NATIONAL GUIDELINES ON THE USE OF RAPID DIAGNOSISTIC TESTS _RDT'S

Document Sample
NATIONAL GUIDELINES ON THE USE OF RAPID DIAGNOSISTIC TESTS _RDT'S Powered By Docstoc
					         NATIONAL GUIDELINES ON THE USE OF RAPID
      DIAGNOSISTIC TESTS (RDT’S) IN THE DIAGNOSIS OF
                        MALARIA

1.0    INTRODUCTION

       Early diagnosis and treatment are key to addressing morbidity and
       mortality due to malaria. The development of Rapid Diagnostic
       Tests (RDT‟s) over the past decade has offered the potential for the
       extension of accurate diagnosis to remote and poorly resourced
       areas that are beyond the reach of high quality microscopy
       services. Rising drug costs and recognition of the inaccuracy of
       clinical diagnosis are increasing the demand for demonstration of
       parasitaemia prior to therapy.

       The high cost of artemisinin-based combination therapies (ACTs)
       compared to that of previously recommended medicines had led
       countries in Asia and Latin America, where malaria transmission
       is low to strengthen parasite-based diagnostic facilities so that
       cost savings may be made by treating with ACTs only those
       individuals with a positive parasitological diagnosis. This has led
       to RDTs being deployed at the periphery of the health services,
       including at community level, and in the private sector.

1.1    Background of Malaria Rapid Diagnostic Tests

       Malaria RTDs, sometimes called “dipsticks” on “malaria rapid
       diagnostic devices”, assist in the diagnosis of malaria by providing
       evidence of the presence of malaria parasites in human blood.
       RTDs have a place as an alternative to diagnosis based on clinical
       grounds or microscopy in some situations, particularly where good
       quality microscopy services cannot be readily provided. Changes
       in treatment policies to more expensive multi drug regimes are
       increasing the importance of obtaining an accurate diagnosis
       based on demonstration of parasitemia prior to treatment.

1.2    What is a Malaria Rapid Diagnostic Test (RDT)?

       Malaria RDTs detect specific antigens (proteins) produced by
       malaria parasites, which are present in the blood of infected or
       recently infected individuals (other “RDTs” that detect antibodies
       are used for screening blood for evidence of recent infection, and
       are not discussed here.). Some RDTs can detect only one species
       (Plasmodium falciparum) some detect more than one species.



                                                                         1
      Blood for the test is commonly obtained from a finger prick. RDTs
      are an alternative to diagnosis based on microscopy.

      When used correctly, malaria RDTs can provide a useful guide to
      the presence of clinically significant malaria infection caused by
      the species of parasite they are designed to detect. RDTs can help
      in case management, particularly when good quality microscopy-
      based diagnosis is unavailable.

1.3   Mechanism of action of malaria rapid diagnostic tests

      RDTs are lateral flow “Immuno-chromatographic” antigen –
      detection tests, which rely on the capture of dye-labeled antibodies
      to produce a visible band on a strip of nitro-cellulose. With
      malaria RDTs, the dye labeled antibody first binds to a parasite
      antigen, and the resultant complex is captured on the strip by a
      band of bound antibody, forming a visible line (test line). A control
      line gives information on the integrity of the antibody-dye
      conjugate, but does not confirm the ability to detect parasite
      antigen.

      The first step of the test procedure involves mixing the patients
      blood with a lying agent in a test strip or well. This ruptures the
      red cells, releasing more parasite protein, labeled antibody, either
      in the well or on the strip, may then bind the target protein
      (antigen).

      The resulting mixture of blood products and antigen-labelled
      antibody complex then passes along the nitro-cellulose strip. This
      is facilitated partly by capillary action through the fiber-mesh of
      the strip, and partly by flushing with a fluid buffer placed behind
      the blood. It passes over the test and control bands.

      The free, labeled antibody will capture the parasite antigen if
      present which will in turn be captured by the test-band
      antibody. The accumulation of microscopic dye particles on the
      thin band produces a visible line if sufficient antigen – labeled
      antibody complex is present.

      The control band will come visible as sufficient labeled antibody
      accumulates on the line. Antibody (or antigen) bound to the strip
      captures labeled antibodies which failed to bond to antigen from
      the patient‟s blood. A visible control line indicates that labeled
      antibody has traversed the full length of the strip, past the test
      line, and that at least some free antibody remains conjugated to



                                                                         2
       the dye and that some of the capturing properties of the antibodies
       remain intact.

       The intensity of the test band will vary with the amount of antigen
       present, at least at low parasite densities (antigen concentration),
       as this will determine the amount of dye particles which will
       accumulate on the line.        The control band intensity may
       decrease at higher parasite densities, as much of the labeled
       antibody will have been captured by the test band before
       reaching the control.

1.4    Types of Malaria Rapid Diagnostic Tests

       The three main groups of antigens detected by commercially
       available RDTs are:
       Histamine - rich protein 2 (HRP2), specific to P. falciparum.
       Plasmodium lactate dehydrogenase (pLDH) currently used in
         products that include P. falciparum – specific, pan-specific, and
         P.vivax specific pLDH antibodies.
       Aldolase (pan specific).

 Target antigens of commercially available malaria rapid diagnostic
                              tests.



                                HRP2            pLDH         Aldolase
p. falciparum specific          +               +



Pan specific (all species)                      +                  +

P. vivax – specific                             +




Most commercial products include antibodies to:
   HRP2 alone (P. falciparum)
   HRP2 and aldolase (distinguishing P. falciparum/mixed infection
      from non-falciparum alone).




                                                                         3
      Falciparum – specific LDH and pan-specific LDU (distinguishing P.
       faciparum mixed infection from non-falciparum alone).
      HRP2 and pan-specific LDH.
      HRP2, pan-specific pLDH and vivax-specific pLDH or Pan-specific
       aldolase only.

RDT detecting both falciparum – specific and non-falciparum (or pan-
specific) target antigens are commonly called combination or “combo”
tests.

The products come in various formats like:
   Plastic cassette
   Card
   Dipstick
   Hybrid cassette-dipsticks.

In areas where only falciparum malaria occurs, or non-falciparum
malaria rarely occurs without co-infection of P.falciparum, RDTs that
detect only P. falciparum are generally preferable on grounds of lower
cost. Most (or all) commercially – available RDTs in this category detect
HRP2.

1.5    Advantages and Disadvantages of HRP2 RDTs

Advantages:
   No need for laboratory facilities
   Simplicity and rapidity of the tests.
   No need for electricity or laboratory equipment.
   Minimal requirement for training (basic skills acquired in 1 day).
   Acceptable levels of sensitivity and specificity, and
   Feedback of conditions of use can be provided to manufactures.

Disadvantages:
    More expensive than microscopy.
    Limitations in species identification, and
    Persistent positively of HRP2 tests after effective treatment.

1.6    Transportation chain and storage of RDTs.

1.6.1 Transportation: Maintaining a “cool chain”.

      The development of a “cool chain” for shipment and storage of
       RDTs is essential.




                                                                         4
       Environmental conditions during transportation can be extreme,
       and every precaution should be taken to avoid RDTs being kept in
       conditions of excessive heat or humidity.
       Transport from the manufacturer and road transport within a
       country, are particularly vulnerable times. Avoid leaving RDTs in
       vehicles parked in the sun.

1.6.2 Stability and Storage:
    Proteins are denatured by heat, and RDTs are thus susceptible to
      being inactivated through exposure to excessive heat. Exposing
      RDTs to temperatures of 0ºC and below may also cause damage.
    Most manufacturers recommend RDT storage between 2ºC and
      30ºC. Expiry dates are generally set according to these conditions.
      If kits are stored at temperatures exceeding the recommended
      limits, it is likely that the shelf life of the RDTs will be reduced and
      sensitivity lost prior to the expiry date.
    All RDTs should remain sealed until immediately before use. If
      stored in a cool environment, they should be allowed to reach room
      temperature before being opened to avoid condensation forming on
      the strip.

1.7    Who should perform RDTs
      Most of the current RDTs are designed for ease of use. It seems
       clear that it is possible to train unskilled – but willing – individuals
       to become reliable competent in the use of RDTs.
      With adequate training, (usually 1 day), Health Care Auxilliary
       staff, Family Welfare Educators, nurses, and doctors, can use
       RDTs effectively, achieving acceptable high sensitivity and
       specificity, comparable with the results obtained by an experienced
       microscopist.




                                                                             5
2.0    PROCUREMENT OF RDTs


2.1    Important factors to be considered when choosing the RDTS:

   Sensitivity should be near 95% at 100 parasites /ul for detection of
    p.falciparum. Specificity should be close to 90%.
   A minimum shelf of 18 months to two years is the appropriate
    requirement.
   In most remote endemic areas, storage temperatures above 30 will be
    unavoidable, hence temperature should range from 2 to 30 degrees
    Centigrade.
   RDTS for field use in tropical conditions should be individually
    packaged in moisture- proof envelopes, which should remain sealed
    until immediately prior to use.

2.2    The procurement unit should request the following from
       suppliers /manufactures doing the tendering process.

   ISO certification and GMP procedures
   Real –time temperature stability data on the product.
   Evidence of successful operational use or good quality field trial data
    on the product.
   Provision of sample product for assessment and testing for ease of use
    (user- friendliness). .
   Box sizes appropriate to the rate of use of tests in the intended area
    and to minimize uncontrolled storage and need to split boxes.

2.3    Evaluation and report on RDTs conduced in 2006 is shown in
       appendix 1.




                                                                         6
                    QUALITY ASSURANCE OF RDTS


3.0 INTRODUCTION

Variation in RDT accuracy in published trials and operational experience
underline the need for an accurate transport system for monitoring the
accuracy of RDTs after release by the manufacture. The Development of
a comprehensive quality assurance scheme is essential to ensure that
test quality is maintained, reducing the likelihood of misdiagnosis and
maintaining confidence of health service providers and consumers. In
time such a scheme will provide standardized evidence of test
performance to guide purchasing and development.


3.1   Malaria RDTs are affected by various conditions of manufacture,
      storage and use that can impair their accuracy and reliability. The
      Global initiative to scale up introduction of RDTs to aid in the
      management of malaria, especially in the locations where
      microscopic based diagnosis is unavailable therefore requires a
      system in place to assure that service quality is guaranteed.

3.2   QA is defined as a total process both in and outside the lab
      including performance standards, good lab practice and
      management skills to achieve and maintain a quality service and
      provide for continuing improvement.

3.3   The purpose of QA is to provide reliable, relevant, timely test
      results that are interpreted correctly thereby increasing efficiency,
      effectiveness, enhancing patient satisfaction and decreasing costs
      brought about by misdiagnosis.

3.4   This is increasingly important with the advert of combination
      therapies and their higher associated costs. A QA process for
      malaria RDTs should aim to ensure high accuracy of tests in the
      hands of end-users. This will include both monitoring of the
      technical standard of the RDTs, process to minimize
      environmental insult training and monitoring of preparation and
      interpretation by end- users.

3.5   Quality control must be practical, achievable and affordable. There
      has to be a system for laboratory- based assessment of
      performance of RDTs throughout their shelf- life and beyond.


                                                                         7
QUALITY CONTROL AND THE END USER:


4.1   The degree to which individual countries /malaria control
      programmes implement RDT/QA schemes will depend on practical
      and organizational issues.

4.2   The QA focus at this level should concentrate on initial training,
      supervision and continuous education so that personnel working
      remote areas achieve and retain competence and motivation.
      Training should not only include test procedure methodology but
      also trouble shooting.

4.3   TRAINING

The QA concept includes the notion that the personnel have sufficient
education, training and experience to permit the proper performance of
duties. This later concept becomes more difficult to implement at lower
levels of the chain. A QA scheme is only as strong as the weakest link in
the chain; therefore everyone involved should receive appropriate and
rapid feedback to maintain commitment to the programme.              The
importance of end user performance to the accuracy of malaria RDT
cannot be over emphasized. Ideally training may              consists of
instructions received on the job but most importantly through formal
training.

     The following should be emphasized during training and after
implementation:

   Exercising diligence in the performance of assigned duties.
   Maintaining a required level of proficiency.
   Exercising judgment /seeking advice in reacting to unforeseen
    circumstances.
   Keeping accurate records.
   Requesting necessary training.
   Honesty and
   Motivation

4.4   To maintain a quality service, the initial training must be
      supplemented by regular supervision and in-service courses. An
      organized system of supervision, that is       periodic visits by
      experienced staff, especially to peripheral areas will provide a


                                                                       8
      mechanism by which problems are discussed, and resolved and
      anomalies in reported results are investigated.

4.5   Supervisors themselves must be adequately trained so that
      supervision is carried out in a helpful, constructive way and is not
      just a critical analysis.

4.6   Training on performance and interpretation of results shall be
      done annually through the period of September to November and is
      a continuous process.

4.7   If need be training will be done in the local language.

4.8   TRANSPORT AND STORAGE OF RDTS. (SEE PARAGRAPH
      1.6.1)

These demand a „cool chain‟ transport and storage, and are important
for:

     Careful coordination of transport to avoid unnecessary delays
      between C.M.S. and the end user.
     Avoidance of exposure to direct sunlight.
     Use of air conditioned /refrigeration storage where possible
      (frequently impossible in peripheral areas.)
     Temp monitoring of storage facilities.
     Rejection of RDTs where packaging is significantly damaged and it
      is likely that moisture- proofing of envelops or canisters is lost.
      Use of cooler boxes and icepacks for transport to remote areas.


5.0. QUALITY CONTROL


5.1   RDTs and slides should be run in parallel with particular
      emphasis on good record keeping so as to compare results.

5.2   Records will be inspected on monthly basis to see if any correlation
      or disparities.

5.3   Henceforth communication between supervisor and end –user will
      be initiated.

5.4   Evaluation of the new-kits will be done every 24 months.




                                                                        9
6.0    OTHER ISSUES


6.1    Operational problems that might be encountered include the
       following:

   Supply delays, resulting in stock outs

   Delayed disownments and limitation of funds for procurement.

   Delays between peripheral and control levels in re-ordering of
    supplies.

   Transport /distribution problems (no temperature control for RDTS
    and no fuel for vehicles).

   Poor storage conditions at the peripheral levels.

   Difficulty in ordering specific product and consumer pressure for
    treatment despite a negative RDT result.


7.0    RECOMMENDATION

It is recommended that one or two people should be designated to
coordinate RDT QA at a national level, coordinating transport, storage,
provision of samples for testing, and with oversight of training and
monitoring of users.




                                                                     10
Appendix 1

EVALUATION REPORT OF MALARIA RAPID DIGNOSTIC TEST (RDTS)

1.0    INTRODUCTION

Parasitological confirmation of clinical diagnosis in malaria infections
should be part of good clinical practice to improve the quality of care.
However, where microscopy is not possible, Rapid diagnostic test (RDTs)
should be used and appropriate Quality Assurance Systems be
established. On this basic fact, we asked the suppliers to submit the
malaria rapid diagnostic kits for evaluation. These kits were of two
types:

    RDT Specifically detecting plasmodium falciparum infections only
    RDT detecting both falciparum- specific and non-falciparum (or pan-
     specific commonly called combination or „combo‟ tests.

Where plasmodium falciparum is the predominant species (>90%),RDTs
that can detect only p.falciparum are appropriate. In areas where P.
vivax accounts for a significant proportion of the cases of malaria
disease, a test that detects falciparum plus pan-malaria antigens or
falciparum species is preferable.

2.0    TYPES OF KITS SUBMITTED

Kits that were specific for plasmodium falciparum detection included the
following:

1.    Vision Bioteck- currently in use.
2.    Paracheck- ORCHID.
3.    Malaria Quick test- Cypress diagnostics.
4.    Care start.
5.    Core-Malaria PF.
6.    Smart check.
7.    Advantage Malaria card.
8.     Forest fast.
9.     NEOBIO Malascan.

Kits that were pan- specific (combo kits) included the following:

1.     Hexagon –Human.
2.     Malaria Total Quick test –Cypress Diagnonstics.



                                                                       11
3.       Parascreen –Zephyr Biomedical

3.0      FACTORS CONSIDERED

Important considerations involved choosing an RDT include:

    Sensitivity and specificity.

Ideally, detection of parasites antigens by RDTS should be at least as
sensitive as detection of parasite by microscopy, 95c% sensitivity at a
parasite density of 100/ul of blood is recommended.

    Stability and storage.

     -      Proteins are denatured by heat, and RDTs are thus susceptible
            to being inactivated through exposure to excessive heat.
     -      Exposing RDTs to temperatures below 0 degrees Centigrade
            and below may also cause damage.
     -      High humidity will also adversely affects RDTs.
     -      It is important that RDTs have a reasonably long shelf –life.
            WHO recommends a minimum shelf –life of 18 months to 2
            years.

    Ease of use

     -      This impacts on sensitivity and stability.
     -      One of the prerequisites for the acceptability of RDTs for use in
            the field is ease of use, and most current RDTs are designed to
            ensure this.
     -      With adequate training, it is expected that village malaria
            workers and health volunteers, medical assistants and nurse
            aids can use RDTs effectively, achieving similar acceptable high
            sensitivity and specificity.

    Cost

     This will be evaluated when the suppliers‟ bids for the item during
     tender procedures.

     4.0       FINDINGS

     The following kits were positively recommended for use.
     1. Vision Bioteck.
     2. Paracheck –ORCHID.
     3. Malaria Quick test- Cypress Diagnostics.


                                                                           12
  4.   Smartcheck .
  5.   Advantage Malaria card.
  6.   Care start.
  7.   Core- Malaria PF.
  8.   Hexagon (Combo) - Human.

  The fortress fast was not evaluated due to low infection malaria rate
  reported by the facility where it was sent.



  5.0       CONCLUSION

  The suppliers whose kits have been recommended will be informed so
  that they can bid for the product during the tender.

  Report complied by:
  Dr I. M. Mtoni           - Consultant Microbiologist- NHL

  Mr T.J. Senosi              -     Scientist and Technical Supervisor-
  NHL

  Mr T.R Bowe             -         Chief Medical Laboratory
  Technicians- CMS

30th January 2007




                                                                          13

				
DOCUMENT INFO