The most appropriate additional intervention in this patient is to treat her partner. This patient has the characteristic features of frothy yellow discharge, burning, and dyspareunia associated with infection by Trichomonas vaginalis organisms, which are seen on microscopy. Trichomoniasis is the most common curable sexually transmitted infection (STI) worldwide and is evenly distributed among women of all age groups, unlike other STIs that predominate in younger people. It is caused by motile flagellated protozoa that infect the urogenital tract, causing inflammatory vaginitis and urethritis. Treatment with a single 2-g dose of metronidazole is associated with a high rate of cure and should be offered to all symptomatic women. It is important that sexual partners also be treated, even if asymptomatic, because of a high rate of reinfection; documentation of infection is not required before treatment in any partners. Once trichomoniasis is identified, testing for other STIs should be considered in both individuals.

Trichomoniasis has been traditionally associated with a vaginal pH of greater than 4.5 and diagnosed by direct visualization of trichomonads on saline microscopy. However, the specificity of a high vaginal pH and the sensitivity of saline microscopy findings are low. Therefore, point-of-care vaginal swab rapid immunoassays and nucleic acid amplification tests (NAATs) for detection of T. vaginalis are increasingly considered to be the gold standard for diagnosis, and particularly when microscopy is not available. NAATs can be performed on a vaginal (or endocervical) swab, urine sample, or liquid-based Pap test specimens. In this patient in whom trichomonads are seen on microscopy, confirmatory testing with another assay is not necessary.

Trichomoniasis causes an inflammatory vaginitis, and cervical contact bleeding may occur due to inflammation from the infection. This inflammation resolves with treatment of the infection, and a follow-up Pap smear to detect cervical pathology would not be required in the absence of additional symptoms or findings.

Treatment of trichomoniasis with single-dose metronidazole is highly effective; therefore, testing for cure is not required in patients whose symptoms have resolved with therapy.