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Background: Rescreening women for Trichomonas vaginalis (TV) infections is important as repeat infections are common, ranging from 5%-31%. Nucleic acid amplification testing (NAAT) too soon after treatment may result in false positives as a result of detection of remnant TV nucleic acids. The goal of this study was to determine the rate of false positive NAAT results at weeks 1-4 post treatment completion using culture as the gold standard.
Methods: Women attending an STI clinic in New Orleans who were InPouch culture positive and treated with metronidazole (MTZ) were included. Participants were scheduled for 4 weeks of follow up visits starting one week post-treatment completion; they provided self-obtained vaginal swabs (SOVS) and information regarding sexual exposure. SOVS were tested using InPouch culture and Gen-Probe Aptima TV (GPATV) assay which targets ribosomal RNA. Women who were culture positive at follow-up were considered re-infected/treatment failure and were not followed further. Incentives were $20 at baseline and $50 at each follow up visit.
Results: To date, 39 women were InPouch+ at baseline and were followed. Of these, 3 (7.7%) were InPouch TV+ at follow-up (1 at 1 week and 2 at 2 weeks) and reported no sexual exposure. Thus, these women were considered likely treatment failures and were no longer followed. Of the remaining cases, 5/29 (17.2%) were GPATV+ at 1 week, and 1/34 (2.9%) was GPATV+ at 2 weeks. All of these women (n=6) were simultaneously InPouch TV-, reported no vaginal sexual exposure, and were InPouch TV-/GPATV- at subsequent visits. No woman was GPATV+ at 3 or 4 weeks.
Conclusions: These data suggest that TV ribosomal RNA has been cleared from the vagina by 3 weeks post completion of successful MTZ treatment and that the GPATV assay can be relied on as a test-of-cure at this point and beyond.