Comparison of wet mount microscopy and PCR against culture for the diagnosis of trichomonas vaginalis among symptomatic females at Mulago Hospital

Abstract

Background: Trichomonas vaginalis (TV)is a protozoan parasite that causes infection in the human urogenital tract. It is a common cause of vaginitis in women, associated with a frothy, malodorous, greenish vaginal discharge. In men infection can display symptoms of urethritis such as urethral discharge and dysuria. Trichomoniasis is associated with health sequelae such as pelvic inflammatory disease, pretermdelivery and low birth weight. It is also strongly associated with promoting HIV sexual transmission.Diagnosis involves clinical symptoms and laboratory investigations that include wet mount Microscopy, PCR and Culture which is the reference standard.Whereas the wet mount preparation has been historically used since 1836 as a cheap approach to detection of TV infection among the symptomatic women, dataon the technical performance of this test and that of a newer one –the PCR assay in the resource limited settings remains poorly known. This study compared the technical performance of PCR and Wet mount microscopy against Culture as a reference standard for the diagnosis of TV among symptomatic female patients attending the STD clinic in Mulago Hospital, Uganda. Methods: Three vaginal swabs were collected by a clinician from each patient; one used for wet mount preparation, the second for inoculation of TV Inpouch media and the third for PCR. Results were analysed using ms excel, SPSS, and Metadisc software to determine the descriptive statics as well as thediagnostic accuracy measurements Results: The sensitivity, specificity, and kappa agreement of the in-house PCR were 89% (95% CI, 40.0 - 97.2), 99 % (95% CI, 95.3 - 100) and 0.88, respectively. Corresponding values for the Wet mount microscopy were 33% (95% CI, 7.5 - 70.1), 100 (96.9-100.0) and 0.481, respectively. Conclusion: The in-house PCR technique is a highly accurate tool for the direct diagnosis of Trichomonas vaginalis from high vaginal swab (HVS) specimens collected from symptomatic females. We recommend a feasibility study with a view of incorporating the in-house PCR tool into routine Clinical Laboratories for rapid and accurate diagnosis of TV.