Comparison of aptima Trichomonas vaginalis transcription-mediated amplification assay and BD affirm VPIII for detection of T. vaginalis in symptomatic women: Performance parameters and epidemiological implications

  • Andrea S
  • Chapin K
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Trichomonas vaginalis is an underestimated sexually transmitted infection (STI) associated with numerous clinical sequelae. The true prevalence and clinical impact of trichomoniasis are unknown, as current methods of detection exhibit poor sensitivity compared to molecular amplification methods. Limited data exist com-paring the BD Affirm VPIII hybridization assay to the Gen-Probe Aptima T. vaginalis (ATV) transcription-mediated amplification (TMA) assay for detection of T. vaginalis. In this study, specimens from 766 patients were evaluated. Specimens were retrieved consecutively from patients with vaginal complaints and/or with histories suggestive of STI. Study inclusion was dependent upon the request for and collection of both a vaginal swab for Affirm and a specimen for Aptima Combo 2 by the health care provider during the same office visit. Affirm was performed using the specific collection swab and the transport provided for the test. The ATV assay was performed on remnant Aptima Combo 2 specimens. A second ATV TMA assay, utilizing an alternate T. vaginalis primer and probe set, was performed on all specimens positive by the initial TMA and/or the Affirm assay. Infected-patient status was defined as positive T. vaginalis test results by at least 2 assays. Overall, 5.1% of subjects were positive for T. vaginalis. T. vaginalis was most prevalent in women who were 36 to 45 (11.9%), 51 to 60 (7.7%), and 16 to 25 (4.2%) years of age. The ATV assay was statistically more sensitive than the Affirm assay (100% versus 63.4%, P < 0.0001), identifying 36.6% more positive patients. Despite a worldwide prevalence rate likely to be double that of Neisseria gonorrhea and Chlamydia trachomatis combined, Trichomonas vaginalis is not currently a reportable disease in the United States (1, 7). Recent literature suggests an associ-ation between T. vaginalis infection and the sequelae of other sexually transmitted infections (STIs), including low birth weight, premature rupture of membranes, preterm labor, atyp-ical pelvic inflammatory disease, infertility, prolonged carriage of human papillomavirus (HPV), and an increased risk for acquiring HIV (9, 10, 13, 18, 21, 31, 32). Current methods used for the diagnosis of T. vaginalis, including wet mount micros-copy, rapid antigen testing, and culture, have been shown to have poor sensitivity compared to molecular amplification methods (6, 14, 17, 19, 24, 25, 27). In addition, variable per-formance occurs with antigen testing and wet mount micros-copy, depending on whether patients are symptomatic or asymptomatic (17, 26). The BD Affirm VPIII (Affirm) assay (Becton Dickinson, Sparks, MD) is the only Food and Drug Administration (FDA)-cleared, direct-specimen, RNA probe-based diagnostic test designed to differentiate and identify pathogens associated with bacterial vaginosis (Gardnerella vaginalis) and vaginitis (T. vaginalis and Candida species). The Affirm test is widely used, yet limited data exist comparing this test with other molecular methods (5). The purpose of this study was to evaluate the performance parameters of the BD Affirm assay with the Gen-Probe Aptima Trichomonas vaginalis (ATV) assay, a molecular diagnostic assay that uses transcription-mediated amplification (TMA) for the detection of T. vaginalis. The ATV assay recently com-pleted clinical trials and has been submitted to the FDA for clearance. Samples were collected from a female population for whom Chlamydia trachomatis, Neisseria gonorrhea, and T. vaginalis testing was being performed due to presentation of symptoms of G. vaginalis or because of a history of STIs. T. vaginalis prevalence by age in the population tested was com-pared to those of C. trachomatis and N. gonorrhea. The popu-lation assessed is considered a low-prevalence population for both C. trachomatis and N. gonorrhea (28). (Preliminary findings were presented as a poster at the 110th General Meeting of the American Society for Microbiology, San Diego, CA, 23 to 27 May 2010 [3].)

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  • Sarah B. Andrea

  • Kimberle C. Chapin

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