Population size, HIV, and behavior among MSM in Luanda, Angola: challenges and findings in the first ever HIV and syphilis biological and behavioral survey.

OBJECTIVES: To conduct the first population size estimation and biological and behavioral surveillance survey among men who have sex with men (MSM) in Angola.
DESIGN: Population size estimation with multiplier method and a cross-sectional study using respondent-driven sampling.
SETTING: Luanda Province, Angola. Study was conducted in a large hospital. PARTICIPANTS: Seven hundred ninety-two self-identified MSM accepted a unique object for population size estimation. Three hundred fifty-one MSM were recruited with respondent-driven sampling for biological and behavioral surveillance survey.
METHODS: Interviews and testing for HIV and syphilis were conducted on-site. Analysis used Respondent-Driven Sampling Analysis Tool and STATA 11.0. Univariate, bivariate, and multivariate analyses examined factors associated with HIV and unprotected sex. Six imputation strategies were used for missing data for those refusing to test for HIV. MAIN OUTCOME: A population size of 6236 MSM was estimated. Twenty-seven of 351 individuals were tested positive. Adjusted HIV prevalence was 3.7% (8.7% crude). With imputation, HIV seroprevalence was estimated between 3.8% [95% confidence interval (CI): 1.6 to 6.5] and 10.5% (95% CI: 5.6 to 15.3). Being older than 25 (odds ratio = 10.8, 95% CI: 3.5 to 32.8) and having suffered episodes of homophobia (odds ratio = 12.7, 95% CI: 3.2 to 49.6) significantly increased the chance of HIV seropositivity.
CONCLUSIONS: Risk behaviors are widely reported, but HIV seroprevalence is lower than expected. The difference between crude and adjusted values was mostly due to treatment of missing values in Respondent-Driven Sampling Analysis Tool. Solutions are proposed in this article. Although concerns were raised about feasibility and adverse outcomes for MSM, the study was successfully and rapidly completed with no adverse effects.