Multi-dose metronidazole treatment for Trichomonas vaginalis more effective than single-dose treatment in clinical practice: A retrospective cohort study.

BACKGROUND: Trichomonas vaginalis (TV) is the most prevalent non-viral sexually transmitted infection (STI) globally. The objective of this study was to estimate the effectiveness of multi-dose metronidazole treatment on repeat TV test positivity in pregnant and non-pregnant women. METHODS: This retrospective cohort study used electronic medical record data and included patients testing positive for TV by nucleic acid amplification test between July 2020 and June 2022 at a large safety-net hospital in the Southeast United States. The primary exposure was treatment type (no treatment, single-dose metronidazole, multi-dose metronidazole), and the outcome was a repeat positive TV test between 4 and 20 weeks after the initial test. Covariates included demographic characteristics, substance use, pregnancy, and concurrent STI. Log-binomial regression modeling estimated the association between treatment type and repeat positive TV test. RESULTS: Of 1,583 women with a positive TV test during the study period, 66% were under the age of 35, 96% self-identified as Black, and 39% were pregnant. Only 487 women (31%) had a repeat test performed, and 26% of these (n=125) had TV on repeat testing. Compared with multi-dose treatment, both no treatment and single-dose treatment were associated with higher risk of repeat positive TV test (RR 2.43; 95% CI 1.48, 4.01 and RR 1.44; 95% CI 1.05, 1.99, respectively). CONCLUSIONS: Repeat test rates were low and repeat TV positivity was high. Multi-dose metronidazole was superior to single-dose treatment. Strategies to increase repeat testing and address high repeat positivity should be undertaken in routine clinical settings.