Re: WHO criteria for accepting positive PCR test -amendment
Re: WHO criteria for accepting positive PCR test -amendment
WHO criteria for accepting positive PCR test results of H5 infection in humans from national reference laboratories
Amendment 30 August 2007
English [pdf 68kb]
Amendment ● 30 August 2007
Laboratory testing is the only way to confirm that infection with H5 influenza viruses has occurred and is critical for both national H5N1 surveillance activities as well as optimal clinical care in this current period when H5N1 infections remain sporadic. WHO has published recommended laboratory tests to use for confirming influenza A(H5) infectioniii and guidance on the interpretation of test resultsiv. Among these tests, polymerase chain reaction (PCR) is the most common approach used by most laboratories to confirm H5 infection.
However, testing for H5 influenza virus infections is not done routinely by many laboratories. Among laboratories that do test for H5, the levels of experience and diagnostic capacities can vary.
This document provides the necessary criteria by which WHO will accept country reported H5 positive PCR test results as "confirmed".
All countries are urged to share with WHO all H5 positive specimens/virus isolates from humans so that analyses of pandemic risk, development of H5 vaccines, development and updating of diagnostic protocols and reagents, monitoring of antiviral susceptibility patterns and other important risk assessment and response activities can proceed.
WHO will accept H5 positive PCR test results from national reference laboratories as follows:
1. Results are accepted from a national reference laboratory that is also a WHO H5 Reference Laboratoryv.
2. Results are accepted from other national reference laboratories (a) that have participated in the WHO External Quality
Assessment (EQA) Projectvi for the detection of subtype influenza A viruses by polymerase chain reaction (PCR) testing, and that have achieved excellent results with the use of the most recent test panel provided by the EQA Project, demonstrated by the correct detection of all H5 viruses and the absence of any false H5 positive results;
and (b) that also have had, in the period since 2004, direct experience in testing for human - 1 -
H5 influenza virus infections and that have made at least 3 positive H5 diagnoses, of which all have been confirmed by WHO H5 Reference Laboratories.
3. Countries that do not yet have a national reference laboratory, or whose national reference laboratory is neither a WHO H5 Reference Laboratory nor able to fulfill the complete criteria listed under 2., must have its positive H5 test results confirmed through referral of samples for re-testing at a) a WHO H5 Reference Laboratory; or b) a national reference laboratory from which H5 testing results are accepted by WHO.
4. In exceptional situations WHO may decide that there is need for follow up investigation of the results received from a laboratory that fulfills criteria 1. to 3. above. In such situations, e.g. if there is a sudden increase in positive H5 test results that does not appear to reflect the epidemiologic situation in the country, staff from WHO Headquarters, relevant Regional Offices or Country Offices will work with the national reference laboratory to further review the situation.
All countries are encouraged to participate routinely in the WHO EQA Project to accumulate and maintain H5 testing proficiency skills. WHO will periodically review these criteria and may change them in the future as indicated.
