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Recently treated Trichomonas vaginalis infection with a prematurely positive post-treatment NAAT — DFSRH MCQ

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HardTrichomoniasisRecently treated Trichomonas vaginalis infection with a prematurely positive post-treatment NAATDFSRH

A 29-year-old woman requests insertion of a 52 mg levonorgestrel intrauterine device. Pregnancy is reasonably excluded. Three weeks ago, vaginal NAAT confirmed Trichomonas vaginalis infection. She completed metronidazole 400 mg twice daily for 7 days with full adherence and no vomiting; the course ended 10 days ago. Her discharge and vulval soreness have resolved. Her current partner completed treatment concurrently, and they abstained from sexual contact until 7 days after both had finished treatment. She reports no other sexual partners. A repeat vaginal NAAT, arranged as a test of cure 10 days after completion of metronidazole, is positive for T. vaginalis. Tests for Chlamydia trachomatis and Neisseria gonorrhoeae are negative. She is afebrile and has no pelvic pain, abnormal discharge, purulent cervicitis, uterine or adnexal tenderness, or cervical excitation. Which is the most appropriate management plan?

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Correct answer: C — Insert the intrauterine device today, give no further antimicrobial treatment now, and repeat NAAT at least 21 days after the original course

The positive NAAT was obtained only 10 days after multidose metronidazole. At this interval, remnant T. vaginalis nucleic acid may remain detectable despite eradication of viable organisms. Evidence suggests waiting at least 21 days after completion of multidose treatment before NAAT-based reassessment. Adherence, symptom resolution, concurrent partner treatment and absence of subsequent exposure make immediate reinfection or established treatment failure less likely. Insertion need not be delayed. FSRH classifies current trichomonal vaginitis as UKMEC 2 for both copper and levonorgestrel intrauterine contraception and states that treatment should be given but insertion can proceed without delay. She has completed treatment and has no cervicitis or PID features. A incorrectly treats trichomoniasis like an insertion-contraindicating bacterial STI. B exposes her to unnecessary repeat treatment on the basis of a prematurely obtained NAAT. C similarly assumes treatment failure; escalation or susceptibility assessment is considered only after genuine persistence has been established and reinfection and non-adherence excluded. E correctly permits insertion but ignores an uninterpretable positive result; appropriately timed repeat testing is needed to determine whether infection persists.

Reference: FSRH Clinical Guideline: Intrauterine Contraception (March 2023; amended January 2025) — https://www.fsrh.org/Common/Uploaded%20files/documents/fsrh-clinical-guideline-intrauterine-contraception-mar-23-amended.pdf Optimal Timing for Trichomonas vaginalis Test of Cure Using Nucleic Acid Amplification Testing (2019) — https://pubmed.ncbi.nlm.nih.gov/30601374/ Trichomoniasis (Reviewed 16 July 2025) — https://www.nhs.uk/conditions/trichomoniasis/