No evidence of an increase in serosorting with casual partners among HIV-negative gay men in London, 1998-2005.

Serosorting is an HIV risk reduction strategy whereby some gay men only engage in unprotected anal intercourse with casual partners of the same HIV status. There was no evidence of an increase in serosorting among HIV-negative gay men in London between 1998 and 2005 (1.7%, 1.2%; test for a trend P = 0.1). By way of comparison, the percentage of HIV-positive gay men who reported serosorting more than doubled during this time (6.8%, 17.7%, P < 0.01).