High Prevalence of Sexually Transmitted Infections and Poor Sensitivity and Specificity of Screening Algorithms for Chlamydia and Gonorrhea Among Female Sex Workers in Zimbabwe: Analysis of Respondent-Driven Sampling Surveys in 3 Communities.

Background: Effective strategies to reduce sexually transmitted infection burden and transmission among female sex workers (FSWs) and their networks are needed. We report sexually transmitted infection prevalence among FSWs in Zimbabwe and investigate the performance of screening algorithms.

Methods: Respondent-driven sampling (RDS) surveys, including blood sampling for syphilis serology, were conducted among FSWs in 3 communities in Zimbabwe in 2017. In addition, a random sample of one-third of participants were offered genital examination and sexually transmitted infection (STI) testing. Data on symptoms and clinical signs were analyzed to determine the proportion of asymptomatic and clinically inapparent STIs by HIV status, and the sensitivity, specificity, and predictive values of syndromic, clinical, and hybrid screening algorithms for chlamydia and gonorrhea. Analyses were RDS-II weighted.

Results: Overall, 2507 women were included in the RDS surveys, and 661 of 836 (79.1%) of those randomly offered genital examination and STI testing accepted. The prevalence of STI by site ranged from 15.7% to 20.0% for syphilis (rapid plasma reagin + Treponema pallidum hemagglutination assay), 6.8% to 14.3% for gonorrhea, 8.4% to 10.1% for chlamydia, 26.6% to 35.5% for trichomonas, and 37.0% to 47.6% for any high-risk human papilloma virus. A high proportion of infections were both asymptomatic and clinically undetectable (gonorrhea: 41.2%, chlamydia: 51.7%, trichomonas: 62.8%). Screening algorithms performed poorly whether based on symptoms only (sensitivity: 53.3% gonorrhea, 43.3% chlamydia) or either symptoms or clinical signs (sensitivity: 58.7% gonorrhea, 48.3% chlamydia).

Conclusions: Sexually transmitted infection burden is high among FSWs in Zimbabwe. The low sensitivity and specificity of screening algorithms used to guide syndromic management mean that more effective approaches are required to strengthen STI control. As access to HIV-specific prevention methods like preexposure prophylaxis increases, support for consistent condom use needs to be strengthened.