Serosorting, the practice of seeking to engage in unprotected anal intercourse with partners of the same HIV status as oneself, has been increasing among men who have sex with men. However, the effectiveness of serosorting as a strategy to reduce HIV risk is unclear, especially since it depends on the frequency of HIV testing.
We estimated the relative risk of HIV acquisition associated with serosorting compared with not serosorting by using a mathematical model, informed by detailed behavioral data from a highly studied cohort of gay men.
We demonstrate that serosorting is unlikely to be highly beneficial in many populations of men who have sex with men, especially where the prevalence of undiagnosed HIV infections is relatively high. We find that serosorting is only beneficial in reducing the relative risk of HIV transmission if the prevalence of undiagnosed HIV infections is less than ∼20% and ∼40%, in populations of high (70%) and low (20%) treatment rates, respectively, even though treatment reduces the absolute risk of HIV transmission. Serosorting can be expected to lead to increased risk of HIV acquisition in many settings. In settings with low HIV testing rates serosorting can more than double the risk of HIV acquisition.
Therefore caution should be taken before endorsing the practice of serosorting. It is very important to continue promotion of frequent HIV testing and condom use, particularly among people at high risk.
In this article we describe the relative risk of acquiring HIV associated with serosorting and determine that serosorting is only beneficial in settings with very high testing rates. Supplemental digital content is available in the article.
From the National Centre in HIV Epidemiology and Clinical Research, Faculty of Medicine, The University of New South Wales, Sydney, Australia
We acknowledge funding from the Australian Research Council (DP0771620) and the National Health and Medical Research Council (CDA568705). The National Centre in HIV Epidemiology and Clinical Research is funded by the Australian Government Department of Health and Ageing, and is affiliated with the Faculty of Medicine, University of New South Wales.
Correspondence: David P. Wilson, PHD, Level 2, 376 Victoria Street, Darlinghurst, Sydney, NSW 2010, Australia. E-mail: email@example.com.
Received for publication March 4, 2009, and accepted June 14, 2009.
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