Early promise of dried blood-spot test to monitor HIV treatment in less-developed countries

Preliminary findings in this week's issue of THE LANCET suggest that a simple enzyme-based procedure to measure CD4+ lymphocytes-important in assessing individuals' responses to antiretroviral treatment-could be possible with the analysis of dried blood spots on filter paper. Such assessment could be invaluable as antiretroviral drugs become available in less-developed countries where laboratory based CD4 cell count assessment is unrealistic.

CD4+ lymphocyte measurement is essential in guiding antiretroviral therapy for patients with HIV-1 infection. Low CD4+ counts indicate a need for intensive therapy, and the establishment of CD4+ counts above 200 cells per milliliter of blood (achievable with antiretrovirals) indicates reasonable immune function. Alimuddin Zumla from University College London, UK, and colleagues at the University Teaching Hospital, Lusaka, Zambia, obtained blood from 42 HIV-1-infected Zambian patients. Blood spots were dried on filter paper and CD4+ lymphocyte counts were measured with a commercial enzyme immunoassay. The investigators compared these measurements with those obtained with standard flow cytometry-the laboratory 'gold standard' for CD4+ assessment.

Results of the filter-paper method compared well with flow cytometry CD4 counts greater than 200 cells/mL. The investigators conclude that dried whole blood stored on filter paper could be developed into a field-friendly alternative for CD4+ lymphocyte count measurements.

Alimuddin Zumla comments: "Many African countries are now introducing antiretroviral therapy to their HIV-infected populations. The monitoring of this treatment requires CD4 count measurement which unfortunately is currently not available to the majority of poor people living away from cities where the health clinics and hospitals are based. Furthermore, the current method of testing is expensive. Our results are very encouraging as they point the way towards making cheap CD4 count testing easily available to people receiving antiretroviral therapy in rural areas. Such methods could be used in a similar way towards HIV viral-load measurements, another test required to assess the success of HIV treatment." (quote by e-mail; does not appear in published paper).

Contact: Professor Alimuddin Zumla, Centre for Infectious Diseases & International Health, University College, London, Windeyer Institute of Medical Sciences, Room G41, 46 Cleveland Street, LONDON, W1P 6DB, UK;
T)44-207-679-9311;
F)44-207-679-9311;
E) a.zumla@ucl.ac.uk

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