Our purpose was to determine the reliability of the Pap smear in making the diagnosis of bacterial vaginosis and to examine the characteristics of Pap smear vs vaginal culture in diagnosis of bacterial vaginosis, with the vaginal Gram stain used as the diagnostic standard. We performed a prospective, blinded study involving 245 women who referred to the Department of Gynecology and Obstetrics in our hospital for routine genital examination between September 2001 and September 2002. Exclusion criteria included vaginal bleeding and pregnancy. Each patient had standard Pap smear, Gram-stained vaginal smear and culture of vaginal swab. The sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic value of Pap smear and vaginal culture results were determined with Gram stain used as the standard for diagnosis of bacterial vaginosis. Using Gram stain diagnosis of bacterial vaginosis as the standard, Pap smear and vaginal culture test results had sensitivity of 43.1 and 77.8%, specificity of 93.6 and 97.7%, positive predictive value of 73.8 and 93.3%, negative predictive value of 79.8 and 91.4%, diagnostic value of 78.8 and 91.8%, respectively, for the diagnosis of bacterial vaginosis. Compared to the microbiological test results, Pap smear is not sensitive enough for screening of bacterial vaginosis. However, because of its high specificity, it may be an adequate diagnostic criteria when it is positive.
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