Diagnosis of bacterial vaginosis in cases of abnormal vaginal discharge: comparison of clinical and microbiological criteria

Introduction: Bacterial vaginosis is a polymicrobial syndrome involving replacement of normal vaginal hydrogen peroxide producing lactobacilli by a variety of mycoplasmas and Gram-negative rods. Bacterial vaginosis has been conventionally diagnosed using Amsel criteria (a clinical method) or Nugent's score (a laboratory method with higher reproducibility). This study was undertaken to compare the diagnostic ability of the Amsel criteria with that of Nugent's score among patients presenting with abnormal vaginal discharge. Methodology: The study was conducted at the Medical College in Kolkata, India to determine the prevalence of patients with bacterial vaginosis and their demographic profile. Subjects attending the outpatient department presenting with abnormal vaginal discharge were evaluated for the presence of bacterial vaginosis by Amsel criteria and Nugent's score. Results: Prevalence of bacterial vaginosis was 24% by Nugent's score. In comparison, Amsel criteria had sensitivity of 66.67%, specificity of 94.74%, positive predictive value of 80% and negative predictive value of 90%. There was no perfect inter-rater agreement between the Amsel criteria and Nugent's score (Kappa = 0.58). Presence of clue cells correlated best with a positive diagnosis by Nugent's score while the amine test (whiff test) had the lowest correlation. Conclusion: Although the Amsel criteria method is a convenient and inexpensive means of diagnosing bacterial vaginosis, it is not always reliable. Alternative reliable and inexpensive diagnostic methods that unify clinical and microbiological parameters, thus increasing sensitivity while retaining specificity, are needed.