First principle: read the fingerprint, not the colour
Reproductive‑age vaginal health depends on Lactobacillus‑dominant, acidic flora. The three common syndromes have distinct signatures:
| Feature | Bacterial vaginosis | Trichomoniasis | Candidiasis |
|---|---|---|---|
| Nature | dysbiosis (not inflammation) | protozoal STI | fungal |
| Discharge | thin, homogeneous grey‑white | frothy, yellow‑green | thick, curdy white |
| Odour | fishy | malodorous | not fishy |
| Itch/inflammation | minimal | present | marked |
| pH | >4.5 | >4.5 | <4.5 |
| Microscopy | clue cells | motile trichomonads | yeast/hyphae/pseudohyphae |
| Classic sign | positive whiff | strawberry cervix | vulval erythema/excoriation |
| Partner Rx | no | yes | no |
Diagnostic anchors
- BV — Amsel (3 of 4): thin discharge, pH >4.5, clue cells, positive whiff (amine) test. Reference standard = Nugent Gram‑stain score.
- Candida: pH stays <4.5 — a fast discriminator.
- Trichomonas: wet mount is only ~44–68% sensitive and drops with delay → NAAT is far more sensitive. 🚩
Management logic
- BV: metronidazole (oral or vaginal) or clindamycin. Partners not routinely treated.
- Trichomonas: metronidazole (multi‑day preferred in women), treat the partner, retest at ~3 months (reinfection common).
- Candida (uncomplicated): topical azole or single oral fluconazole (non‑pregnant); topical azoles in pregnancy — do not carry forward oral fluconazole for pregnant women.
Pitfalls
- Diagnosing by discharge colour alone (history is insufficient — use pH + microscopy).
- Excluding trichomoniasis on a negative wet mount.
- Treating a partner for candida (unnecessary).
Pearls
- 🎯 BV = clue cells + whiff + pH>4.5; Trich = strawberry cervix + treat partner; Candida = curdy + pH<4.5.
- 🩺 BV and trichomoniasis in pregnancy have adverse associations — don't dismiss them as trivial.
Next → When infection climbs above the cervix (Concept 27).