Diagnostic accuracy of the Xpert CT/NG and OSOM Trichomonas Rapid assays for point-of-care STI testing among young women in South Africa: a cross-sectional study.

ABSTRACT

OBJECTIVES: Syndromic management of sexually transmitted infections (STIs) omits asymptomatic infections, particularly among women. Accurate point-of-care assays may improve STI care in low- and middle-income countries (LMICs). We aimed to evaluate the diagnostic performance of the Xpert Chlamydia trachomatis/Neisseria gonorrhoeae (CT/NG) and OSOM Trichomonas vaginalis (TV) Test as part of a STI care model for young women in South Africa. DESIGN: Diagnostic evaluation conducted as part of a prospective cohort study (CAPRISA 083) between May 2016 and January 2017. SETTING: One large public healthcare facility in central Durban, KwaZulu-Natal, South Africa PARTICIPANTS: 247 women, aged 18-40 years, attending for sexual and reproductive services to the clinic. Pregnant and HIV-positive women were excluded. OUTCOMES: Diagnostic performance of the Xpert CT/NG and OSOM TV assays against the laboratory-based Anyplex II STI-7 Detection. All discordant results were further tested on the Fast Track Diagnostics (FTD) STD9 assay. RESULTS: We obtained vaginal swabs from 247 women and found 96.8% (239/247) concordance between Xpert and Anyplex for CT and 100% (247/247) for NG. All eight discrepant CT results were positive on Xpert, but negative on Anyplex. FTD STD9 confirmed three positive and five negative results, giving a confirmed prevalence of CT 15.0% (95% CI 10.5 to 19.4), NG 4.9% (2.2-7.5) and TV 3.2% (1.0-5.4). Sensitivity and specificity of Xpert CT/NG were 100% (100-100) and 97.6% (95.6-99.7) for CT and 100% (100-100) and 100% (100-100) for NG. The sensitivity and specificity of OSOM TV were 75.0% (45.0-100) and 100% (100-100). CONCLUSION: The Xpert CT/NG showed high accuracy among young South African women and combined with the OSOM TV proved a useful tool in this high HIV/STI burden setting. Further implementation and cost-effectiveness studies are needed to assess the potential role of this assay for diagnostic STI testing in LMICs. TRIAL REGISTRATION NUMBER NCT03407586; Pre-results.