New STI Guidelines: Herpes, Bacterial Vaginosis, and Trichomoniasis

Neil Skolnik, MD


October 07, 2021

This transcript has been edited for clarity.

I'm Dr Neil Skolnik. This is the second installment covering the 2021 CDC Sexually Transmitted Infection Guidelines that were released last month.

Today I'll discuss guideline changes for herpes, trichomonas, and bacterial vaginosis (BV). Last month we posted New STI Guidelines: Chlamydia, Gonorrhea, and Pelvic Inflammatory Disease.

Let's start with herpes. Approximately 12% of adults in the United States are HSV-2 positive, and most do not know they are infected, so most new infections are contracted from a partner who didn't know they were infected. Diagnosis is made initially by visual inspection for the typical clustered vesicles, and then confirmed either by a swab of the lesion and sending it for nucleic acid amplification test (NAAT). The test is very sensitive if the vesicle is intact but the sensitivity decreases rapidly after the vesicle has burst. When you can't get a good sample from a fresh lesion, then type-specific serologic tests can be used to make the diagnosis.

It's important to understand the limitations of serology. Serology can be falsely negative early on in infection, so if you suspect a new (first episode) of herpes clinically but the serology is negative, consider repeating serology 12 weeks later. The other caveat is false-positive results. With a specificity of about 60%, you need to put the result in context. With a low index of suspicion for herpes (ie, patient is asymptomatic but wondering if they have herpes), and it comes back positive, there is a reasonable chance that this is a false positive. This is why HSV-2 serology is not recommended as a screening test. Nor is IgM serology recommended for screening because it is also not very specific.

Management is straightforward: acyclovir, famciclovir, or valacyclovir for first episodes. For recurrent episodes, either treat each episode as early on as possible or, more commonly, use suppressive therapy to reduce the rate of transmission.

Let's go on now to BV. BV occurs when there is replacement of normal lactobacillus species in the vagina with high concentrations of anaerobic bacteria, including Gardnerella vaginalis. The diagnosis of BV can be made easily at the point of care: a thin discharge; clue cells on microscopy; a pH of vaginal fluid > 4.5. If uncertain, you can send a sample of the discharge for NAAT, which has excellent sensitivity and specificity of 90% and 85%, respectively. Treatment is straightforward: metronidazole 500 mg orally twice daily for 7 days or metronidazole gel or clindamycin cream. Note that clindamycin cream is oil based and so can weaken latex condoms. Treatment of sexual partners is not recommended for BV. For women with multiple recurrences, either metronidazole gel or suppository twice weekly for > 3 months can be used.

Trichomoniasis is common and can be symptomatic or asymptomatic. In fact, the majority of persons who have trichomoniasis (70%-85%) either have minimal or no genital symptoms, and untreated infections might last from months to years. Diagnosis is usually by wet mount, but it is important to realize that the sensitivity of wet mount is only about 60% compared with culture. If the wet mount is negative and you suspect trichomoniasis, then order a NAAT, which has sensitivity of 95%-100%.

The big news with trichomoniasis is a change in the recommendation for treatment from the old recommendation of metronidazole 2 g as a single dose to the current recommendation of metronidazole 500 mg orally twice a day for 7 days. This change is based on a study showing twice as high a cure rate at 1 month with the 7-day regimen. Treating sexual partners is important.

This is a lot of important, new information.

I'm Dr Neil Skolnik and this is Medscape.

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