Seroadaptive behaviors among Seattle men who have sex with men (MSM): a shift in operationalization, trends, and association with HIV
Many men who have sex with men (MSM) engage in seroadaptive behaviors – i.e., chose their sex partners, selectively use condoms, or adopt a sexual role based on their partner’s HIV sero-status. Some of these behaviors may protect against HIV, but the complexity in measuring seroadaptive behaviors has made it difficult to develop messages about the practice.
In a retrospective records review of MSM attending the Public Health – Seattle & King County (PHSKC) STD clinic and Gay City Health Project (GCHP), we examined trends in sexual behaviors and HIV test positivity between 2002 and 2013. We used log binomial regression to assess the risk of HIV/STI test positivity for serosorting (condomless anal intercourse [CAI] only with HIV-concordant partners) relative to non-concordant CAI (CAI with partners of discordant or unknown status) and no CAI. For an ongoing cross-sectional seroadaptive behaviors study, we developed a computer-based method to automatically recruit and enroll MSM PHSKC clinic patients into the study. We describe the proportion of men who enroll in the study and how these men differ from those who decline to enroll, to gauge the representativeness of our study sample. Using data from the population of enrolled men, we compared the prevalence and agreement (kappa statistic) of four seroadaptive behaviors using two definitions: a behavioral definition (men are classified as engaging in seroadaptive behaviors based on their reported sexual history) versus a purposely-adopted definition (men are specifically asked if they purposely adopted certain behaviors based on their partner’s HIV status, to reduce the risk of HIV acquisition or transmission).
We found that the proportion of men who report serosorting in the prior year increased substantially (by 15%) between 2002 and 2013, and in 2013 nearly one-third to one-half of MSM reported the behavior. Among HIV-negative MSM, these increases were concurrent with significant declines in the proportion of MSM who reported NCCAI, indicating a shift toward generally safer behaviors. Serosorting was associated with a lower risk of HIV than NCCAI (adjusted relative risk [aRR]=0.53; 95% confidence interval [CI]=0.45-0.62) but a higher risk than no CAI (aRR=1.98; 95% CI=1.61-2.44). The absolute risk of testing newly positive for HIV declined for all men (from 3.5% to 1.4%; P=0.001)), regardless of reported behavior. In our cross-sectional seroadaptive behaviors study, we enrolled men at 2,661 (54%) of 4,994 eligible clinic visits during an 18-month period in 2013-2014, including 1,748 unique MSM. Enrolled men were broadly representative of all MSM in the clinic but compared to non-enrolled men, they reported a higher number of male sex partners (11 vs. 8; P<0.001) and were more likely to report methamphetamine use in the prior year (15% vs 8%; P<0.001). However, the HIV test positivity of enrolled and non-enrolled men was similar (1.9% vs. 2.0%; P=0.8). Among 3,410 visits by men enrolled in the study 2013-2015, pure serosorting (choosing partners based on HIV status) was the most commonly reported behavior (31%-47%), regardless of the definition used. We found that the agreement between the two definitions for the four behaviors was only slight to moderate (kappa range: 0.11-0.43) and the concordance varied by behavior – between 15% and 70% who were classified as engaging in seroadaptive behaviors per the behavioral definition also reported purposely-adopting the behaviors based on their partners’ HIV status.
Results from this dissertation suggest that seroadaptive behaviors are common and are increasing. We confirmed prior studies that found that these behaviors represent an intermediate level of HIV risk – they are associated with a lower risk of HIV than NCCAI but a higher risk than no CAI. Thus, these behaviors may be an effective HIV prevention strategy for some men. However, we also noted that using a behavioral definition to measure seroadaptive behaviors likely includes men who did not purposely adopt these behaviors; therefore, additional work is needed to further describe how use of a purposely-adopted definition may effect these risk estimates in order to appropriately counsel men about the risks and/or benefits of these behaviors. Finally, our novel approach to recruitment holds promise for future studies to efficiently recruit or screen a somewhat young and relatively high-risk population of MSM into HIV prevention research.