Researchers at the Johns Hopkins Bloomberg School of Public Health and the University of Zurich, Switzerland, have developed a less-expensive test for monitoring the progression of HIV during the early stages of the disease.

The test, HIV-1 protein 24 (p24) antigen, predicts disease progression and CD4 lymphocyte count and HIV-1 RNA viral load, measurements currently used to determine when to initiate antiretroviral therapy. The study, "Heat-Denatured Human Immunodeficiency Virus Type 1 Protein 24 Antigen: Prognostic Value in Adults with Early-Stage Disease," appeared in the Journal of Infectious Diseases (2002;186(8)1181-1185).

"The test could be used to determine when to initiate antiretroviral therapy in HIV-infected persons," said Timothy R. Sterling, M.D., a study coauthor and assistant professor of epidemiology at Johns Hopkins. "And because it costs much less than both lymphocyte count and HIV-1 RNA viral load, the heat- denatured p24 antigen test could be of particular benefit in developing countries, where the burden of HIV infection is great."

The Johns Hopkins Hospital price for a CD4 lymphocyte count is $88. An HIV-1 RNA level costs $152. The total cost of the p24 antigen test -- roughly $20-$30 -- is much more affordable, especially given that such tests must be performed frequently. The study notes that the p24 test is easy to perform, and storage is less demanding than that required for other tests.

"P24 antigen is a protein in HIV. The test is administered by drawing blood from a patient, heating the plasma, and then measuring the amount of p24 antigen found in the sample. Higher levels of p24 indicate a greater risk of disease progression," Sterling explained.

Four hundred and ninety four injection drug users enrolled in a longitudinal cohort study were evaluated in the five-year test. Researchers obtained blood samples, analyzed them to quantify T-cell subsets, then quantified HIV-1 RNA and p24 antigen in specimens frozen after collection. They also held semiannual follow-up interviews with participants.

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