Serosorting unproven as a an HIV risk-reduction strategy in men who have sex with men

Is serosorting effective in reducing the risk of HIV-infection among men who have sex with men with casual sex partners?

van den Boom W, Konings R, Davidovich U, Sandfort T, Prins M, Stolte IG. J Acquir Immune Defic Syndr. 2013 Nov 20.  [Epub ahead of print]

Background: We investigated the prevalence and protective value of serosorting (i.e., establishing HIV-concordance in advance to practice unprotected anal intercourse [UAI]) with casual partners (CP) among HIV-negative MSM using longitudinal data from 2007 to 2011.

Methods: Men of the Amsterdam Cohort Studies (ACS) were tested biannually for HIV-1 antibodies and filled in questionnaires about sexual behavior in the preceding 6 months. HIV-incidence was examined among men who practiced UAI, UAI with serosorting, or consistent condom use, using Poisson regression.

Results: Of 445 MSM with CPs, 31 seroconverted for HIV during a total follow-up of 1 107 person-years (PY). Overall observed HIV-incidence rate was 2.8/100PY. Consistent condom use was reported in 64%; UAI in 25%; and UAI with serosorting in 11% of the 2 137 follow-up visits. MSM who practiced serosorting were less likely to seroconvert (adjusted Incidence Rate Ratio [aIRR]=0.46; 95% confidence interval [95%CI]=0.13-1.59) than MSM who had UAI, but more likely to seroconvert than MSM who consistently used condoms (aIRR=1.32; 95%CI=0.37-4.62), although differences in both directions were not statistically significant. MSM who consistently used condoms were less likely to seroconvert than MSM who had UAI (aIRR=0.37; 95%CI=0.18-0.77).

Discussion: The protective effect for serosorting we found was not statistically significant. Consistent condom use was found to be most protective against HIV infection. Larger studies are needed to demonstrate whether serosorting with CPs offers sufficient protection against HIV-infection, and if not, why it fails to do so.

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Editor’s notes: Serosorting is the practice of using HIV status as a decision-making tool in sexual behaviour. For example, by selecting a partner of the same HIV status in order to have unprotected intercourse. In this cohort study of men who have sex with men in Amsterdam, there was some evidence that serosorting was more risky than consistent condom use but less risky than unprotected anal intercourse among casual partners.  The number of seroconversions in the study was relatively small (n=31), precluding more conclusive evidence. One of the barriers to serosorting as a strategy to reduce HIV risk is the process of establishing valid HIV seroconcordance between casual partners. The quality of rapid (home) HIV testing is likely to improve and may lead to an increase in self-testing. In this case, serosorting may become an effective additional HIV risk-reduction strategy in MSM. In the meantime, this study highlights the importance of continuing to encourage consistent condom use for anal intercourse with casual partners.

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