Estimating the Size, Sociodemographic Characteristics, and STI Status of Three Key Populations at Risk for HIV Infection in Panama Using Capture–Recapture Methods: The PEMAR Study

Abstract

This study aims to estimate the size, sociodemographic characteristics, and rates of sexually transmitted infections (STIs) in three key populations in Panama in 2018. Key populations included persons who self-identified as men who have sex (MSM), sex workers, and transgender women. Nationwide, trained peers conducted capture and recapture during the last quarter of 2018 at key population social gathering sites. Participants completed a self-administered questionnaire and, optionally, could opt-in for a blood sample to be tested for four STIs (HIV, syphilis, and hepatitides B and C). Population estimates were calculated using the Sightability Model R package. Among the 1,886 consenting participants, 1,715 completed the study procedures (1,278 MSM, 250 sex workers, and 187 transgender women). The median age was 28 (interquartile range 23–36 years) and most participants were single, Latinx, completed at least high school, worked, and earned less than twice the minimum wage per month. The national estimates were 49,966 MSM (3.81% of adult men), 8,326 sex workers (0.63% of adult women), and 3,100 transgender women (118.4 per 100,000 population). Most (77.4%) participants consented for STI testing, which allowed estimation of positivity rates for HIV (10.0%), syphilis (2.0%), and hepatitides B (1.0%) and C (0.1%). Incorporating capture-recapture methods allowed more precise estimates of key population sizes and to characterize their sociodemographic and STI profiles, to be used in programmatic efforts for resource allocation and prevention programs. As an indirect result, we anticipate increased representation and visibility of key populations in population and public health programs.