Matthew R. Golden, MD, MPH; Joanne Stekler, MD, MPH; James P. Hughes, PhD; Robert W. Wood, MD
Abstract and Introduction
Background: Serosorting is the practice of preferentially having sex with partners of concordant HIV status or of selectively using condoms with HIV-discordant partners.
Methods: We evaluated the epidemiology of serosorting among men who have sex with men (MSM) seen in a sexually transmitted disease clinic, Seattle, WA, 2001-2007, and defined the percentage of visits during which MSM tested HIV positive based on whether they reported nonconcordant unprotected anal intercourse (UAI), UAI only with partners thought to be HIV negative (serosorters), no UAI, or no anal intercourse.
Results: Men reported serosorting during 3295 (26%) of 12,449 visits. From 2001 to 2007, the proportion of visits during which men reported serosorting increased (P = 0.02); this change was greater among HIV-infected MSM than among HIV-uninfected MSM. Among men who tested HIV negative in the preceding year, HIV tests were positive in 49 (3.5%) of 1386 who reported nonconcordant UAI, 40 (2.6%) of 1526 serosorters, 28 (1.5%) of 1827 who had only protected anal intercourse, and 0 of 410 who had no anal intercourse (P < 0.0001); 32% of new HIV infections occurred in serosorters. The prevalence of HIV was higher among serosorters tested during 2004-2007 than among those tested during 2001-2003 (0.85% vs. 3.2%, P = 0.03).
Conclusions: Serosorting offers MSM limited protection from HIV.
Studies conducted in the early 1990s documented that men who have sex with men (MSM) use condoms more often with partners of discordant HIV status than with HIV-concordant partners.[1-3] Subsequent reports compared the sexual mixing patterns of HIV-infected and -uninfected MSM and found that MSM disproportionately have sex with partners of the same HIV status,[4,5] an observation that is consistent with findings from studies restricted to either HIV-infected[6-10] or HIV-uninfected MSM.[11,12] More recently, we observed that among HIV-infected MSM receiving medical care at the largest HIV clinic in Seattle, WA, 24% reported that they had decided not to have sex with another man in the last year because that potential partner was HIV negative and that 31% thought that a potential partner decided not to have sex with them because they were HIV infected. These studies document what is now widely referred to as serosorting.
Serosorting is the practice of preferentially having sex with partners of concordant HIV status or of selectively using condoms with HIV-discordant partners. Reports from San Francisco, London, and Sydney suggest that this practice may be increasing,[15-18] and some investigators have suggested that increased serosorting may be responsible for preventing large increases in HIV acquisition rates even as rates of bacterial sexually transmitted diseases (STDs) among MSM have risen dramatically. Responding to the increased attention focused on serosorting, some US health departments have developed or funded online resources to advise MSM and medical providers about the practice.[19,20]
The extent to which serosorting protects HIV-uninfected MSM from acquiring HIV is uncertain. Prospective studies have associated HIV acquisition with having unprotected anal intercourse (UAI) with partners that study subjects believe are HIV uninfected and with the number of HIV-uninfected partners a participant reports. These findings suggest that serosorting does not eliminate the risk of HIV acquisition. In particular, serosorting may fail if people misreport their HIV status, either because they do not know they are infected or because they knowingly mislead partners. Although the limits of serosorting remain ill defined, a mathematical modeling study evaluating the risk of HIV acquisition associated with serosorting suggested that because of the high risk of HIV transmission during the period after initial HIV acquisition, the practice may be more risky than having sex with persons with known, long-standing HIV infection. We evaluated the epidemiology and protective efficacy of serosorting among MSM tested for HIV in Seattle, WA.