Deciphering Intermediate Nugent scores: Utility of Real-time PCR for Bacterial Vaginosis diagnosis

Abstract

Purpose: To optimize real-time PCR assays for diagnosis of Bacterial Vaginosis (BV) and determine cut-off loads by ROC analysis for Gardnerella vaginalis, Atopobium vaginae and Lactobacillus spp. as compared to Nugent scoring (Gold standard) in clinical samples.

Results: Out of 125 women, 34 were positive, 26 intermediate and 65 negative for BV by Nugent scoring. All three real-time PCR assays were found to be highly sensitive & specific and AUC suggested excellent diagnostic accuracy. An optimal cut-off was >9.45 × 10³ copies/ ml, >3.34 × 10³ copies/ ml & ≤ 18.63 × 10³ copies/ ml for G. vaginalis, A. vaginae and Lactobacillus spp. respectively, in BV positives. Gram staining and qPCR were discordant only in patients with intermediate scores (n = 26) where qPCR identified 15 (57.69%) as positive and 11 (42.3%) as negative.

Conclusion: PCR-based molecular BV diagnosis is more accurate and can be used for deciphering intermediate Nugent scores.

Keywords: Atopobium vaginae; Bacterial Vaginosis; Gardnerella vaginalis; Lactobacillus spp.; and Receiver Operating Characteristic (ROC) curve; real-time PCR.