In vitro diagnostics and laboratory technology

Frequently asked questions

CD4+T-Cell counting technology
  • What are CD4+ T-cells?
  • What is the CD4+ T-cell count?
  • How are CD4+ T-cells enumerated?
Viral load testing
  • What is HIV-1 Viral Load?
  • How are CD4 and HIV viral load used?
  • How is Viral Load measured?
ELISA tests
  • What is an ELISA test?
Simple/Rapid tests
  • What is a Simple/Rapid test?
  • What is the difference between a ELISA and a Simple/Rapid test?
Confirmatory assays
  • What is a Confirmatory Assay?
Window period
  • What is the "window-period" and how long is it?
Alternative specimens- whole blood, oral fluid & urine
  • Is urine or saliva feasible to use as a source of HIV detection?


Request for Proposals

22 MARCH 2017

The Prequalification Team is publishing a request for proposals for consultancy services relating to - developing and maintaining the Quality Management Systems (QMS) and assuming the responsibility for on-going system maintenance and effectiveness of operations within the Prequalification Team.

The services required by the World Health Organization (WHO) are more fully described in the below attached Terms of Reference and Request for Proposals.

Proposals should be submitted to WHO in writing no later than 5 April 2017 at 17:00 hours Geneva time ("the closing date"), by email at the following address:


Contact us

Prequalification Team - Diagnostics
Regulation of Medicines and other Health Technologies
Department of Essential Medicines and Health Products
World Health Organization
20 Avenue Appia
1211, Geneva 27