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Hot Topics in Sexually Transmitted Infections and Associated Conditions

(Published November 2013)


  • Key facts about infection
    • It is caused by the protozoan Trichomonas vaginalis.
    • It is one of the most common STIs in the United States, with an estimated 148,000 new cases each year and a prevalence of about 500,000.2
    • Typical symptoms in women include a diffuse, malodorous, yellow-green vaginal discharge with vulvar irritation; however, infection is common.
    • Men are generally asymptomatic but may have nongonococcal urethritis (NGU).
  • Screening and diagnosis
    • Women presenting with vaginal discharge should be tested for T. vaginalis.
    • Asymptomatic women at high risk for infection should be considered for screening, especially in pregnancy.
    • Risk factors include9,72
      • new or multiple sex partners
      • current diagnosis of or suspicion of any STI
      • history of transactional sex
      • injection drug use
      • African American race/ethnicity
    • Oral infection and isolated rectal infection are rare; testing of extragenital sites is not recommended.9,73
    • Testing options for women include the following:
      • NAATs are maximally sensitive and are the preferred method for both screening and diagnostic testing. Two assays are currently available:
          • Polymerase chain reaction (Amplicor, Roche)
          • Transcription-mediated amplification (APTIMA T. vaginalis, Hologic Gen-Probe)
          • Preferred samples: vaginal swab in women, urine in men
          • Same-day or next-day result
      • Culture
          • Previously the gold standard; misses 20 to 30 percent of vaginal infections.
          • Vaginal swab or fluid, very insensitive for male urine.
          • Results take up to five days.
  • Saline microscopy (wet prep)
  • Historically the most common test, but only 50 to 60 percent sensitive, that is, misses half of all symptomatic infections in women and almost all asymptomatic ones
  • Useful for rapid diagnosis by clinicians (where microscopy is CLIA-approved)
  • Not suitable for testing males
      • POCT
          • Antigen tests
            • Example: OSOM (Sekisui Diagnostics), uses immunochromatographic capillary flow dipstick technology
            • Results available in about 10 minutes
          • Nucleic acid probe tests
            • Example: Affirm VP III (Becton Dickenson), simultaneously evaluates for T. vaginalis, Gardnerella Vaginalis (an aid to diagnosis of BV), and Candida albicans
            • Results available in about 45 minutes
    • Testing options for men include the following:
      • No POCTs or NAATs are currently FDA approved for use in men.
      • Wet prep and culture are currently the only approved testing modalities, but they miss most infections.
      • Thus, practically speaking, there are no tests available for men that are both sensitive and cost-effective.
  • Treatment and management
    • Recommended regimens include the following:

Table 17: Recommended Regimens for the Treatment of Trichomoniasis9

Medication Dosage and Duration Comments
(Flagyl® and generics)
 2 g orally, single dose Approximate efficacy 9095%
2 g orally, single dose Approximate efficacy 86100%
Metronidazole 500 mg orally twice daily for 7 days Improved efficacy for patients who will comply with complete regimen; preferred in HIV-infected patients
Tinidazole 500 mg orally twice daily for 5 days  
  • Multidose regimens (i.e., 57 days) have superior efficacy compared with single-dose regimens. Single-dose treatment is preferred if compliance with multiple dose therapy is uncertain.74
  • Patients should be advised to avoid the consumption of alcohol while taking either drug and for 24 hours after completing metronidazole or 72 hours after completing tinidazole.
  • Note that both drugs are nitroimidazoles and allergic cross-reactivity may exist; there is no evidence that tinidazole can be safely used in patients with metroniadazole allergy.
  • Intravaginal treatment (e.g., metronidazole gel) is unreliable and not recommended.