The tampon test for trichomoniasis: A comparison between conventional methods and a polymerase chain reaction for Trichomonas vaginalis in women

Objectives: Trichomonas vaginalis is the most common STD worldwide and the infection has been linked with an increased risk of HIV transmission. We present a detailed comparison between conventional collection and testing methods and the polymerase chain reaction (PCR) tampon test for T vaginalis. Methods: Women were tested for the presence of T vaginalis by PCR analysis of a tampon specimen and by conventional methods which included one or more of the following: culture and microscopy from a high vaginal swab (HVS) or endocervical swab (ECS), and microscopy of a Papanicolaou (Pap) smear. Results: T vaginalis was detected in 51/590 (8.6%) conventional tests and 93/590 (15.8%) tampon specimens. Retesting of all tampon PCR positive specimens confirmed 89/93 (95.7%) tests. Using the tampon PCR as the reference, the sensitivities of the different conventional sampling and testing methods for the detection of T vaginalis were 8.3% (5/60) for ECS microscopy or culture, 31% (13/42) for HVS microscopy or culture, 52.8% (19/36) for HVS directly inoculated into Trichomonas medium and 59.4% (38/64) for Pap smear. Conclusions: No conventional test in the remote setting has comparable sensitivity to PCR. The Pap smear is the next most sensitive, but requires a speculum examination. The use of PCR will allow inclusion of T vaginalis into STD screening programmes in both developed (lower prevalence) and developing (higher prevalence) countries.