A 24-year-old woman comes to the office due to copious green vaginal discharge and burning with urination for 3 days. The patient had a yeast infection a year ago, which was treated with over-the-counter medication. She has recently become sexually active with a new partner and occasionally uses condoms. Physical examination shows a yellow-green, frothy vaginal discharge and diffuse vaginal erythema but no lesions. The uterus is anteverted with no cervical motion tenderness. Which of the following is the best test to confirm the diagnosis in this patient?
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The most likely cause of this patient's abnormal vaginal discharge is Trichomonas vaginalis, a sexually transmitted infection that often presents with a malodorous, thin, frothy, yellow-green vaginal discharge. The trichomonads infect the squamous epithelium of the vagina, resulting in vulvovaginal inflammation and subsequent vulvar pruritus, dyspareunia, vulvovaginal erythema, and discharge.
Wet mount saline microscopy of trichomoniasis typically shows characteristic motile, flagellated protozoans. Nucleic acid amplification testing can also be performed and is the gold standard. Treatment of the patient and the patient's sexual partners is with metronidazole.
(Choice A) Cervical cytology (ie, Pap test) is a screening test for cervical cancer. Most patients with high-grade cervical lesions or cervical cancer are asymptomatic; patients with symptoms typically present with postcoital bleeding or a mucopurulent cervical discharge with an associated cervical lesion.
(Choice B) Neisseria gonorrhoeae is a common sexually transmitted infection that may present with mucopurulent (not frothy) vaginal discharge originating from an inflamed cervix. A Gram stain may show gram-negative diplococci in polymorphonuclear leukocytes. Gram staining is not performed for T vaginalis because the process often changes the organism's shape, making it difficult to identify.
(Choice C and E) pH and whiff tests can be used to diagnose bacterial vaginosis, which typically presents with thin, off-white, malodorous discharge with no associated vaginitis. In bacterial vaginosis, the addition of potassium hydroxide (KOH) to the vaginal discharge releases amines, causing a characteristic odor (eg, positive whiff test). Vaginal pH is elevated in both bacterial vaginosis and trichomonas infection; therefore, pH testing is not specific for diagnosis.
(Choice D) Urine culture is used to diagnose urinary tract infections, which can present with dysuria; however, patients do not have associated vaginal discharge.
Educational objective:
Trichomonas vaginalis is a sexually transmitted motile protozoan which can be seen on wet mount microscopy of vaginal discharge. It presents with yellow-green, frothy vaginal discharge and vulvovaginal erythema.