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
Garrett N., Mitchev N., Osman F., Naidoo J., Dorward J., Singh R., Ngobese H., Rompalo A., Mlisana K., Mindel A.
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- A nd 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.