34 yo F presents for WH appt. Feels well, reports mild non-purulent vaginal discharge x2 months. Monogamous x4 years, no hx of STI. Speculum exam normal, wet mount/koh prep negative. Pap returns normal except rare trichomonas. What next?
1. Intravaginal metronidazole gel (0.75%) once daily for five days
2. Metronidazole 2g po xi
3. Metronidazole 500mg po BID x7d and treat partner
4. New specimen for Fungal and T. vaginalis Cultures -Correct Answer
This is a healthy patient with questionable symptoms (her discharge may also be physiologic). She is not in a high risk group, and trichmononas, though a common disease, is an unlikely cause in this patient and is a surprising finding. The most common vaginal discharges are BV, Trich and Candida. Of the "bedside" tests, the Wet Mount has the best sensitivity (clue cells:sensitivity 98.2%, specificity 94.3%, positive predictive value 89.9%, negative predictive value 99.0%). The Whiff Test is also relatively sensitive. BV is thus ruled out by the the findings. Of note Intravaingal Metronidazole is a treatment only for BV, not TV.
KOH prep is not particularly sensitive 60% for vulvovaginal candidasisis (a more likely Dx than Trich in this patient). If symptoms persist, it may be reasonable to send for gram stain/fungal culture in this patient to clarify the diagnosis. Also fungal culture is indicated if patient has failed Rx for candida to look for non-abicans species.
Wet mount is not particularly sensitive for T. vaginalis (40–70%), especially if there is time lag in sample transport. Trich is likely under diagnosed as a result, and further investigation is warranted, especially in patients treated for Candida or BV (without partner treatment-as males are almost always asymptomatic). The wet mount does have good specificity for Trich. Patients with history of STIs should be investigated for T. vaginalis (along with CT/GC) if they have any symptoms of discharge. Any patient that is diagnosed with T. Vaginalis should have partner treatment as well to reduce risk of re-infection, and barrier methods should be used until treatment is complete.
However, in this case we have the opposite situation. We doubt the diagnosis of TV as it did not show up on bedside tests and the patient is not high risk. The specificity of cytology for trich is such that in an endemic area or high risk population, treatment can be based upon a positive result, but not in low risk/low endemic area. In this case, it's reasonable for us to use a more sensitive and specific test for trichomonas: either culture or PCR to confirm diagnosis. In addition, fungal culture would help rule out candidaisis.
Sherrard J, Donders G, White D, Jensen JS; European IUSTI. European (IUSTI/WHO) guideline on the management of vaginal discharge, 2011. Int J STD AIDS. 2011 Aug;22(8):421-9.
