title: Trends in Serosorting and the Association With HIV/STI Risk Over Time Among Men Who Have Sex With Men.
abstract: Serosorting among men who have sex with men (MSM) is common, but recent data to describe trends in serosorting are limited. How serosorting affects population-level trends in HIV and other sexually transmitted infection (STI) risk is largely unknown.
  
  
  
  We collected data as part of routine care from MSM attending a sexually transmitted disease clinic (2002-2013) and a community-based HIV/sexually transmitted disease testing center (2004-2013) in Seattle, WA. MSM were asked about condom use with HIV-positive, HIV-negative, and unknown-status partners in the prior 12 months. We classified behaviors into 4 mutually exclusive categories: no anal intercourse (AI); consistent condom use (always used condoms for AI); serosorting [condom-less anal intercourse (CAI) only with HIV-concordant partners]; and nonconcordant CAI (CAI with HIV-discordant/unknown-status partners; NCCAI).
  
  
  
  Behavioral data were complete for 49,912 clinic visits. Serosorting increased significantly among both HIV-positive and HIV-negative men over the study period. This increase in serosorting was concurrent with a decrease in NCCAI among HIV-negative MSM, but a decrease in consistent condom use among HIV-positive MSM. Adjusting for time since last negative HIV test, the risk of testing HIV positive during the study period decreased among MSM who reported NCCAI (7.1%-2.8%; P= 0.02), serosorting (2.4%-1.3%; P = 0.17), and no CAI (1.5%-0.7%; P = 0.01). Serosorting was associated with a 47% lower risk of testing HIV positive compared with NCCAI (adjusted prevalence ratio = 0.53; 95% confidence interval: 0.45 to 0.62).
  
  
  
  Between 2002 and 2013, serosorting increased and NCCAI decreased among Seattle MSM. These changes paralleled a decline in HIV test positivity among MSM.
authors.affiliation: Departments of *Epidemiology; †Medicine; ‡Biostatistics; §Global Health, University of Washington, Seattle, WA; ‖Public Health-Seattle and King County HIV/STD Program, Seattle, WA; and ¶Gay City Health Project, Seattle, WA.
authors.forename: Christine M
authors.initials: CM
authors.lastname: Khosropour
authors.forename: Julia C
authors.initials: JC
authors.lastname: Dombrowski
authors.forename: Fred
authors.initials: F
authors.lastname: Swanson
authors.forename: Roxanne P
authors.initials: RP
authors.lastname: Kerani
authors.forename: David A
authors.initials: DA
authors.lastname: Katz
authors.forename: Lindley A
authors.initials: LA
authors.lastname: Barbee
authors.forename: James P
authors.initials: JP
authors.lastname: Hughes
authors.forename: Lisa E
authors.initials: LE
authors.lastname: Manhart
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Golden
mesh_terms: D000328:Adult; D017280:Condoms / Q000706:statistics & numerical data*; D006679:HIV Seropositivity; D059147:HIV Serosorting / Q000523:psychology / Q000706:statistics & numerical data*; D018451:Homosexuality, Male / Q000523:psychology / Q000706:statistics & numerical data; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012309:Risk-Taking; D012725:Sexual Behavior / Q000523:psychology / Q000706:statistics & numerical data*; D012747:Sexual Partners / Q000523:psychology*; D012749:Sexually Transmitted Diseases / Q000453:epidemiology / Q000517:prevention & control* / Q000523:psychology; D014861:Washington / Q000453:epidemiology