Evaluation of Various Diagnostic Strategies for Bacterial Vaginosis, Including a New Approach Based on MALDI-TOF Mass Spectrometry

Bacterial vaginosis (BV) is a common dysbiosis of unclear etiology but with potential consequences representing a public health problem. The diagnostic strategies vary widely. The Amsel criteria and Nugent score have obvious limitations, while molecular biology techniques are expensive and not yet widespread. We set out to evaluate different diagnostic strategies from vaginal samples using (1) a combination of abnormal vaginal discharge and vaginal pH > 4.5; (2) the Amsel-like criteria (replacing the "whiff test" with "malodorous discharge"); (3) the Nugent score; (4) the molecular quantification of Fannyhessea vaginae and Gardnerella vaginalis (qPCR); (5) and MALDI-TOF mass spectrometry (we also refer to it as "VAGI-TOF"). Overall, 54/129 patients (42%) were diagnosed with BV using the combination of vaginal discharge and pH, 46/118 (39%) using the Amsel-like criteria, 31/130 (24%) using qPCR, 32/130 (25%) using "VAGI-TOF", and 23/84 (27%) using the Nugent score (not including the 26 (31%) with intermediate flora). Of the 84 women for whom the five diagnostic strategies were performed, the diagnosis of BV was considered for 38% using the combination of vaginal discharge and pH, 34.5% using the Amsel-like criteria, 27% using the Nugent score, 25% using qPCR, and 25% using "VAGI-TOF". When qPCR was considered as the reference, the sensitivity rate for BV was 76.2% for the combination of vaginal discharge and pH, 90.5% for the Amsel-like criteria, 95.2% for the Nugent score, and 90.5% for "VAGI-TOF", while the specificity rates were 74.6%, 84.1%, 95.3%, and 95.3%, respectively. When the Nugent score was considered as the reference, the sensitivity for BV was 69.6% for the combination of vaginal discharge and pH, 82.6% for the Amsel-like criteria, 87% for qPCR, and 78.7% for "VAGI-TOF", while the specificity rates were 80%, 94.3%, 100%, and 97.1%, respectively. Overall, the use of qPCR and "VAGI-TOF" provided a consistent diagnosis of BV, followed by the Nugent score. If qPCR seems tedious and for some costly, "VAGI-TOF" could be an inexpensive, practical, and less time-consuming alternative.