Comparison between Nugent's and Hay/Ison scoring criteria for the diagnosis of Bacterial Vaginosis in WASP prepared vaginal samples

Background: The aim of this study was to compare two different Bacterial Vaginosis diagnosis criteria, Nugent’s score system and Hay/Ison criterion, by using Gram-stained vaginal smears. Materials and findings: Gram-stained smears were prepared with 10 μl and 30 μl of 100 vaginal samples, collected in ESwab®, by the WASP® automatic system. All smears were examined at 1000X magnification and assessed using both Nugent and Hay/Ison criteria. In addition, the presence of clue cells was recorded. All the slides were assessed by two different readers and reviewed by a supervisor. Considering the 10 μl smears, Nugent’s scoring results were: 90 patients with normal vaginal flora, five with intermediate flora and five with Bacterial Vaginosis. Instead, Hay/Ison criterion results were: 83 patients had Grade I, 12 Grade II and 5 Grade III. About the 30 μl ESwab® smears, the Nugent’s scoring results were: 92 patients with normal vaginal flora, three intermediate flora and five with Bacterial Vaginosis. In contrast, the results obtained by using the Hay/Ison criterion were: 84 patients had Grade I, 12 had Grade II and 4 had Grade III. Clue cells were detected in all the Bacterial Vaginosis cases. Conclusions: The Hay/Ison criterion is a credible alternative to the Nugent’s score system for the diagnosis of Bacterial Vaginosis. Furthermore, the combination of WASP® automatic system and the Hay/Ison criterion can represent a fast and reliable workflow, especially in those laboratories where the request of vaginal culture tests is extremely high.