Use of DNA hybridization test for diagnosing bacterial vaginosis in women with symptoms suggestive of infection

The purpose of this study was to evaluate a DNA hybridization test (Affirm VPIII) as an alternative to Gram stain for the rapid diagnosis of bacterial vaginosis in women with clinical signs of vaginal infection. Vaginal specimens were collected from 321 symptomatic women, and analyzed for bacterial vaginosis by both Gram stain using Nugent criteria and DNA hybridization test. Sensitivity, specificity, positive predictive value, and negative predictive value of the DNA hybridization test were determined using the Gram staining as the standard for diagnosis of bacterial vaginosis. Of the 321 patients, 115 (35.8%) were Gram positive for bacterial vaginosis and 126 (39.2%) were negative. 80 patients (25.0%) demonstrated intermediate Gram staining that was also considered negative. The Affirm system detected G. vaginalis in 107 (93.0%) of 115 vaginal specimens positive for bacterial vaginosis diagnosed by Gram stain. Compared to the Gram stain, DNA hybridization test had a sensitivity of 87.7% and a specificity of 96.0%. Positive and negative predictive values of the DNA hybridization test were 93.0% and 92.7%, respectively. In conclusion, Affirm VPIII hybridization test correlated well with Gram stain and may be used as a rapid diagnostic tool to exclude bacterial vaginosis in women with genital complaints.