High prevalence of sexually transmitted infections and poor sensitivity and specificity of screening algorithms for Chlamydia and Gonorrhoea among female sex workers in Zimbabwe: Analysis of respondent-driven sampling surveys in 3 communities

Abstract

Abstract Background: Effective strategies to reduce STI burden and transmission among female sex workers (FSW) and their networks are needed. We report STI prevalence among FSW in Zimbabwe and investigate the performance of screening algorithms. Methods: Respondent-driven sampling (RDS) surveys, including blood sampling for syphilis serology, were conducted among FSW in three communities in Zimbabwe in 2017. Additionally, a random sample of one third of participants were offered genital examination and STI testing. Data on symptoms and clinical signs were analysed 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 gonorrhoea. Analyses were RDS-II weighted. Results: Overall, 2507 women were included in the RDS surveys and 661/836 (79.1%) of those randomly offered genital examination and STI testing accepted. STI prevalence by site ranged from 15.7%–20.0% for syphilis (RPR + TPHA), 6.8%–14.3% for gonorrhoea, 8.4%–10.1% for chlamydia, 26.6%–35.5% for trichomonas, and 37.0%–47.6% for any high-risk human papilloma virus. A high proportion of infections were both asymptomatic and clinically undetectable (gonorrhoea: 41.2%, chlamydia: 51.7%, trichomonas: 62.8%). Screening algorithms performed poorly whether based on symptoms only (sensitivity: 53.3% gonorrhoea, 43.3% chlamydia) or either symptoms or clinical signs (sensitivity: 58.7% gonorrhoea, 48.3% chlamydia). Conclusions: STI burden is high among FSW in Zimbabwe. The low sensitivity and specificity of screening algorithms used to guide syndromic management means that more effective approaches are required to strengthen STI control. As access to HIV-specific prevention methods like PrEP increase, support for consistent condom use need to be strengthened.