A recent laboratory study based on specimens from 766 US patients with vaginal symptoms evaluates the performance of the current US FDA (Federal Drugs Administration) approved diagnostic test for Trichomonas Vaginalis (BD Affirm VPIII hybridization) against a modern molecular amplification based test (Gen-Probe Aptima). The greater sensitivity of the new test emerges clearly in this paper (36.6% more positive patients) – along with a more general message taken up strongly in journalistic reporting of this paper: that the insensitivity of current tests has led to our ignorance of the prevalence and sequelae of Trichomonas, and that the new techniques will require new policies on testing.
Overall prevalence of Trichomonas as against Chlamydia and Gonorrhea turns out much as existing literature would have led us to expect: 5.1%, as opposed to 3.4% and 0.7% respectively. The real surprise comes with the results for age-specific prevalence that show the highest levels of trichomonas positivity (11.9%) occurring among 36-45 year old patents with 0% prevalence for Chlamydia and Gonorroea. The authors’ recommendations for trichomonas testing for age 30+ women along with cervical screening might seem premature at this stage! Nevertheless, the high prevalence among this older group calls for further investigation. The results of this study need replication in a study which gives due attention to considerations beyond those of diagnostic efficacy. Assuming these results to be replicable, and assuming the reliability of the molecular amplification assay with vaginal tissue, there is clearly a challenge here to the widely accepted idea that trichomonas spreads exclusively by sexual transmission. The issue of diagnostic efficacy will need to be integral to future studies, but so will the examination of the full range of epidemiological possibilities. Maybe it is time to dust down some those older theories of transmission via the toilet seat (J.A. Burgess, “Trichomonas Vaginalis Infection from Spashing in Water Closets”, British Journal of Venereal Disease, 39, 1963, pp. 248ff.)!
Sarah B. Andrea & Kimberle C. Chapin, “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”, Journal of Clinical Microbiology, made available in advance of publication
J.A. Burgess, “Trichomonas Vaginalis Infection from Splashing in Water Closets”, British Journal of Venereal Disease, 39, 196