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MOLECULAR TESTING FOR TRICHOMONAS VAGINALIS by Kathleen M. Murphy, Ph.D. & Kenneth E. Youens, M.D. (Download PDF  pdf_button)

Trichomonas vaginalis (TV) is the most common cause of curable sexually transmitted infection in the United States, with an estimated 7.4 million new cases occurring each year. A recent study of the prevalence of TV in the United States reported rates of infection of 8% in women ages 18-39 years, 9-13% in women ages 40-49 years, and 13% in women over 50 years of age. The authors concluded that “The high TV prevalence in all age groups suggests that all women being screened for CT/NG should also be screened for TV.”(1)

Infections in women typically cause vaginitis, urethritis, and cervicitis. Common symptoms include vaginal discharge, vulvovaginal irritation, and/or dysuria, but it is estimated that up to half of TV infections are asymptomatic.(2)

In pregnancy, TV infection increases the risk of premature labor, premature rupture of membranes, and low birth weight.(3) Other manifestations of trichomoniasis include pelvic inflammatory disease, tubal infertility, and rarely, post-abortion or post-hysterectomy infection. 

Diagnosis of TV infection has traditionally been performed by microscopy of vaginal secretions, but this technique requires immediate evaluation of a wet preparation and is only about 60-70% sensitive. Modern nucleic acid-based testing for TV is convenient, accurate, and more sensitive than traditional methods.

trichomonas

Trichomonas vaginalis organisms. Vaginal smear (left) and in in vitro culture (right). Wright-Giemsa stain. (Image source: http://www.dpd.cdc.gov)

 

The Assay Performed at ProPath

The FDA-approved APTIMA Trichomonas vaginalis Assay (Gen-Probe) uses a target amplification method to detect nucleic acid sequences that are specific to TV. The sensitivity and specificity of the test are each reported to be > 99%.(3)

Specimens

  • Liquid-based cytology specimens collected in ThinPrep (PreservCyt) or SurePath media.
  • Endocervical and vaginal swab specimens collected and transported in the APTIMA Unisex collection kit transport medium and tube.

References

  1. Ginocchio et al. Prevalence of Trichomonas vaginalis and co-infection with Chlamydia trachomatis and Deisseria gonorrhea in the United States as determined by the APTIMA Trichomonas vaginalis nucleic acid amplification assay. Abstract presented at the International Society for Sexually Transmitted Diseases Research annual meeting 2011.
  2. http://www.cdc.gov/std/trichomonas.
  3. Cotch MF, Pastorek JG, Nugent RP, et al. Trichomonas vaginalis associated with low birth weight and preterm delivery. The Vaginal Infections and Prematurity Study Group. Sexually transmitted diseases. 1997;24(6):353-60.
  4. Gen-Probe APTIMA Trichomonas vaginalis Assay product insert 502246 rev A.