Abstract #67  -  Are we systematically overestimating sexual risk behaviour? New insights into accurate measurements of risky UAI with casual partners among MSM.
Authors:   Presenting Author:   Mr Wijnand van den Boom - Public Health Service
Additional Authors:  Dr Ineke Stolte, Dr Udi Davidovich,
Aim: In the study of sexual risk behaviour among men who have sex with men (MSM), the term casual partners (CP) was generally used to collectively describe all types of partners that were not considered steady. However, in the perception of MSM, there is a larger diversity of CP which seems to range from a one-time sexual partner to a ‘regular’ sexual partner. We hypothesized that the ability to know the HIV status of a CP will increase the more that CP is a regular one. Therefore, we examined whether higher levels of UAI can be found with a ‘regular’ CP, but due to serosorting, these incidents will be less risky for HIV than with a one-time CP. Thus, the more traditional approach of collectively measuring UAI for all types of CP could cause overestimation of risky UAI.
Method / Issue: In total, 461 HIV-negative tested MSM of the Amsterdam Cohort Study with a mean age of 36 (SD=8; range 18-68) completed a questionnaire inquiring about their condom use with CP, the casual partner’s HIV status and CP type. We measured three CP types: one-time CP (met by chance and had sex with only once), multiple-time CP (met by chance on several occasions and had sex with on these occasions), and ‘regular’ CP (one meets on a regular basis to have sex with; i.e. ‘fuck buddy’). Risky UAI was defined as UAI with a CP with unknown HIV status. Univariate logistic regression analyses were used to examine the association between CP types, and respectively UAI and risky UAI.
Results / Comments: Of all participants, 63% (297/461) had a one-time CP, 34% (156/461) had a multiple-time CP, and 19% (88/461) had a ‘regular’ CP. Prevalence of UAI was 17% (49/297) for one-time CP, 18% (28/156) for multiple-time CP, and 30% (26/88) for ‘regular’ CP. Prevalence of risky UAI was 80% (31/39) for one-time CP, 64% (14/22) for multiple-time CP, and 43% (9/21) for ‘regular’ CP. Univariate analyses indeed revealed that MSM with a ‘regular’ CP were more likely to report UAI than MSM with a one-time CP (OR=2.1; 95%CI 1.2–3.8) or a multiple-time CP (OR=1.8; 95%CI .95–3.48), although the latter was only statistically significant at p<.1. In contrast, MSM with a ‘regular’ CP were less likely to have risky UAI than MSM with a one-time CP (OR=.19; 95%CI .06–.62).
Discussion: In order to accurately measure risky UAI, CP should no longer be considered as one cluster. Our results clearly demonstrate that sexual behaviour at risk for HIV could be overestimated, since a large proportion of UAI with ‘regular’ CP is not risky due to serosorting. Also, because we found a large proportion of risky UAI in one-time CP while this was the most frequently reported type of CP, we suggest to use one-time CP as indicator for sexual risk with CP. Future research should concentrate on validity measurements concerning serostatus knowledge among ‘regular’ CP and whether multiple-time CP should be treated as a separate CP type for the measurement of sexual risk.
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