October 31, 2008
Next month Nature Reviews Microbiology in conjunction with the World Health Organization will publish “Evaluating Diagnostics: the CD4 Guide,” as part of a series of supplements focusing on infectious disease diagnostics. In this issue, DHVI and CHAVI Chief Operating Officer, Tom Denny and Brooke Walker co-author the article titled, “CD4 Immunophenotyping in HIV Infection.” The monitoring of CD4+ T cells during the course of HIV infection is necessary to determine when to initiate antiretroviral therapy (ART) and prophylaxis against opportunistic infections and, just as important, when to change therapy once drug resistance is detected. The authors provide an overview of the historical developments in CD4 enumeration technologies that emerged with the HIV pandemic and address the current technological challenges to make CD4 testing methods more affordable and accessible for developing countries, specifically in sub-Saharan Africa where the highest prevalence of HIV infections occurs.
Advances in CD4 testing methods include taking flow cytometers from the bench into the field such as with hand-held diagnostic CD4 counters that can provide rapid results. Some hand-held technologies are currently being used, but still need to be assessed for accuracy. Other improvements include developing CD4+ T cell counting strategies and gating strategies that are both accurate and precise, but that can also drastically reduce costs within central laboratories. The goal of such technological advances is to allow for point-of-care CD4 testing where results can be obtained in a rural clinic setting, thus reducing the cost and time to transport and process specimens giving the patient more timely treatment.
Improved quality control (QC) and quality assurance (QA) measures are also needed to assess the accuracy of CD4 T-cell subset enumeration strategies, especially when new technologies are introduced to the field. Proficiency testing programs such as DHVI’s Immunology Quality Assessment Center can verify that the accuracy of CD4 counts remains standard across laboratories through the development of validation protocols, standard guidelines, and guidance documents. Such proficiency initiatives help to ensure that laboratory standards are maintained when new CD4 enumeration technologies emerge so that the patient will receive the most effective and timely treatment.
For the full article, please read:
Barnett D, Walker B, Landay AL, Denny TN. CD4 immunophenotyping in HIV infection. Nature Reviews Microbiology
. 2008 November. (6)11: S7-S15. Abstract