What is a characteristic diagnostic finding for Trichomonas vaginalis infection?

• A. Yellow-green discharge with foul odor and normal pH
• B. Yellow-green discharge, elevated pH, and motile flagellated trichomonads on saline prep
• C. White curd-like discharge
• D. Foul odor with itching

Answer: (B)

In Trichomonas vaginalis infection, a telling diagnostic clue is seeing motile, flagellated trophozoites on a saline wet mount, alongside a discharge that is often yellow-green and frothy and a vaginal pH that is elevated above 4.5. The motility of the parasites on the saline preparation is highly characteristic and helps distinguish it from other causes of vaginitis. The elevated pH reflects loss of the protective lactobacilli and the alkalinizing effect of the infection. The yellow-green, frothy discharge fits the typical presentation.

The other descriptions point to different causes: a white curd-like discharge suggests candidiasis, and a foul odor with itching is less specific and can occur with other vaginitis presentations. The combination of a yellow-green discharge, higher pH, and, most importantly, motile flagellated organisms on saline prep, is the best diagnostic clue for this infection.