Infectious Vaginitis Testing
The three most common types of acute vaginitis, accounting for up to 90% of cases, are bacterial vaginosis, candidiasis and trichomoniasis. Differentiation of the causes of vaginitis generally includes microscopic examination of vaginal secretions, commonly termed the wet mount.
Bacterial vaginosis (BV) is the most common cause of acute vaginitis & is believed to be caused by a shift in the normal bacterial flora from a predominance of lactobacilli to mixed flora, including Gardnerella, mycoplasmas, and anaerobes. The diagnosis of BV is suggested by the presence of watery discharge, vaginal pH greater than 4.5, presence of amine odor and “clue cells” on the wet mount. Although vaginal culture is not useful for the diagnosis of BV, candidiasis can be detected either by culture or by presence of hyphae on the wet mount. Likewise, visualization of motile trichomonads on the wet mount is diagnostic of trichomoniasis.
Although the wet mount is a mainstay of diagnosis for vaginitis syndromes, the sensitivity is suboptimal. For example, the sensitivity of wet mount for vaginal candidiasis is reportedly 50% overall, while sensitivity for trichomoniasis is 45-60%. The sensitivity of the wet mount for clue cells is 62 to 93%. The value of microscopic examination for these pathogens is further decreased when there is a delay in specimen transportation.
A DNA probe hybridization test (Affirm VPIII) is now available which simultaneously detects Gardnerella, Candida, and Trichomonas. This test offers significant improvements over microscopy with 92% sensitivity, 99.7% specificity for Trichomonas; 95% sensitivity, 100% specificity for clinically significant levels of Gardnerella; and 82% sensitivity, 98% specificity for Candida.
Vaginal swab specimens should only be submitted in the Affirm Ambient Temperature Transport System.
