HIV-1/2 prevalence among MSM (men who have sex with men) in Eastern and Southern Europe: non invasive oral fluid testing as a tool for surveillance among hard-to-reach groups (reference lab for European Project Sialon p.n. 101046).

Background:MSM account for nearly 40% of all newly diagnosed HIV infections reported in EU in 2008. Since MSM continue to bear a high burden of HIV infection, surveillance data on HIV prevalence among this high risk population are essential for the development and evaluation of HIV control initiatives. The use of oral fluid (OF) has been suggested as an attractive alternative strategy to HIV blood testing for field collection in outreach settings.Objective:This study, involving the participation of seven European countries, was designed primarily to validate a third generation EIA on OF samples from subjects with known HIV serological status and secondly to conduct a European survey for HIV prevalence estimation among MSM from Southern and Eastern countries by means of non-invasive OF sample collection.Methods:On validation study, matched serum and OF samples were collected from both HIV seropositive patients (n=263) and healthy controls (n=235). All samples were analyzed by using Genscreen HIV-1/2 version 2 (BIO-RAD), and procedure was adapted for OF testing by cut-off calculation. A cross sectional-survey was carried out between April 2008 and September 2009, among 2688 MSM accepting to provide OF specimens for HIV antibody testing. A  total IgG quantification test was also performed to ensure that the OF found negative after testing was taken properly.All OF samples were examined using EIA testing and those recording positive EIA results were analyzed for confirmation by a rapid immunocromatographic assay and/or Western Blot. Results: On validation study, all OF sample from HIV positive patients except for 4 samples were positively concordant with serum, whereas a total concordance was found among negative volunteers. This resulted in a sensitivity of 98.5% and a specificity of 100%, when EIA Genscreen was performed on OF samples. We found that cut-off values based on the control sera were also suitable for OF testing (mean±5SD; 0.2). In the multicenter survey, 2535 OF specimens were considered valid for the data analysis. Overall prevalence of antibody to HIV among MSM was 196/2535 (7.7%). A statistically significant difference in HIV prevalence was found between Southern and Eastern European countries (12.3% vs 4.4%; p<0.001).Conclusion: This data indicates that oral fluid based testing is a reliable tool for epidemiological surveillance of HIV infection. High HIV prevalence found among MSM suggests the need for implementation in prevention strategies to control epidemic.