Improved strategies for HIV diagnosis among men who have sex with men (MSM), a high prevalence and incidence population from Buenos Aires, Argentina.

PANDO MA; COLOCCINI RS; SCHVACHSA N; PIPPO M; ALFIE L; MARONE R; GOMEZ CARRILLO M; AVILA MM; SALOMON H

Washington

Conferencia; AIDS 2012; 2012

IAS

Background: In Argentina, HIV diagnosis in adults is made through antibody testing with one or two enzyme immunoassay tests and a confirmatory test (Western Blot, WB). These strategies may ignore infected individuals during early primary infection, representing an important public health problem among groups with high HIV-incidence, such as men who have sex with men (MSM) (6.3% persons/year). The general objective of this study was to contribute to reducing HIV transmission among MSM through the identification of antibody-negative, nucleic acid-positive individuals.  Methods: HIV-negative-WB samples with a discordant screening test and HIV-indeterminate-WB samples were studied for HIV nucleic-acid detection using viral load testing. A group of 241 HIV-negative-samples (with two negative screening assays) was also tested. Results: A total of 1,549 MSM were recruited in an HIV-seroprevalence study. Among those, 161 (10.4%) were HIV-positive and 14 (0.9%) HIV-indeterminate. Among the 1,374 HIV-negative individuals, 16 (1.2%) exhibited reactive results in the screening assay. Indeterminate-WB samples and negative-WB samples (with discordant results in the screening) were analyzed for HIV-nucleic acid detection by viral load testing. Up to 23.1% HIV-indeterminate-WB samples and 7.1% HIV-negative-WB samples with discordant results in the screening assays had detectable nucleic acid. Overall, 14.8% of the samples with discordant or indeterminate results were identified as HIV-positive using direct diagnosis. With the identification of four new cases using nucleic acid detection test, HIV prevalence in MSM increased by 0.3 percent (from 10.4% to 10.7%). Among the HIV-negative samples, no positive cases were detected. Conclusions: Results from this study suggest the importance of including nucleic acid detection in HIV algorithm almost for those HIV-indeterminate-WB and HIV-negative-WB MSM with discordant results in the screening assays. A prospective implementation research study needs to be conducted in order to evaluate the cost-effectiveness of performing nucleic acid detection together with the screening test in this high-risk population.