Evaluation of molecular thresholds based quantification of Gardnerella vaginalis and Fannyhessea vaginae for improved diagnosis of Bacterial Vaginosis.

BACKGROUND

Bacterial Vaginosis (BV) is the most common vaginal infection among reproductive age women. Symptoms based diagnosis using Amsel's criteria lacks specificity. Nugent scoring is regarded as standard method for diagnosis in research settings. However, this method requires specialized training and is quite subjective. Therefore, a standardized molecular assay for BV diagnosis would be of great utility.

METHODS

Vaginal samples (n = 181), classified as positive (n = 39), negative (n = 92) or intermediate (n = 50) based on Nugent scoring, were analyzed for the presence and quantity of two important indicator organisms: G. vaginalis and F. vaginae. Receiver operating characteristics (ROC) analysis was performed to determine quantitative thresholds for each organism. Further, we performed logistic regression to derive a combined diagnostic score.

RESULTS

Application of ROC analysis and logistic regression derived combined quantitative score yielded well balanced sensitivity-specificity profile. The molecular assay categorized 22.8% and 70% Nugent negative and intermediate cases respectively as BV positive, based on bacterial loads substantially exceeding ROC derived thresholds, suggesting possible under detection by microscopy.

CONCLUSION

Overall, this standardized and objective molecular assay is a useful laboratory tool to assist in diagnosis of BV.