Diagnostics and Laboratory Technology

Summary of the study protocol for Multicentre Evaluation of CD4 technologies as part of the WHO Prequalification of Diagnostics Programme (PQDx)

Laboratory evaluation/product testing is one of the components of the WHO prequalification programme. The objective is to compare the performance and ease of use of dedicated and point-of-care CD4+ T-lymphocytes enumeration technologies through conducting a multicentre independent evaluation. Point-of-care CD4 technologies are critical for initiating and monitoring treatment of HIV infected individuals living in low- and middle-income countries.

The study protocol has been cleared by the WHO Ethical Review Committee. Reference laboratories situated in the different WHO regions will participate in the laboratory testing. Fresh venous whole blood specimens collected in EDTA vacutainer tubes submitted for routine CD4 enumeration will be used in the study. The blood specimens will be unlinked and tested following the agreed protocol and in accordance with the manufacturers' instructions for use. Staff will be trained prior to the commencement of the study to ensure proficiency.

Performance evaluation will include:

  • Intra-laboratory variation: intra-assay variation, inter-assay variation, instrument precision and carry-over studies.
  • Agreement between the test method and the reference method which will be a single platform classic flow cytometer.
  • Assessment of the operational characteristics.

The main expected performances of the CD4 technology will include:

  • Intra-assay variation: The %CV less than 15% for CD4 counts less or equal to 200 cells/µl and less than 10% for CD4 counts more than 200 cells/µl.
  • Inter-assay variation: The %CV less than 15% for CD4 counts less or equal to 200 cells/µl and less than 10% for CD4 counts more than 200 cells/µl.
  • Instrument precision: The %CV less than 15% for CD4 counts less or equal to 200 cells/µl and less than 10% for CD4 counts more than 200 cells/µl.
  • Carry-over studies: The carry-over should be less than 2%.

After the studies have been completed, all results will be compiled by WHO, data will be analysed per technology as well as a comparative data set. The analysis will be shared and discussed with the participating laboratories before being finalized. The technology-specific reports will be shared with the respective manufacturers who will be expected to provide comments within 30 days. Final results will then be used in the prequalification programme. A composite report summarizing the results will be published on WHO website.

Contact us

Prequalification Team - Diagnostics
Regulation of Medicines and other Health Technologies
Department of Essential Medicines and Health Products
(HIS/EMP/RHT/PQT)
World Health Organization
20 Avenue Appia
1211, Geneva 27
Switzerland
diagnostics@who.int