Background Current gold standard diagnosis of bacterial vaginosis (BV) relies on categorising Gram-stained vaginal smears through Nugent scoring. We have recently described an alternative method of diagnosis, based on visualisation through fluorescence-in-situ-hybridisation (FISH) of the BV biofilm on desquamated vaginal epithelial cells present in urine sediments.
Methods A vaginal swab and a first void urine specimen were obtained from 72 pregnant women attending the antenatal clinic. The vaginal swab was used to assess the vaginal microbiota status through Nugent scoring. The urine specimen served for FISH-based diagnosis of the Gardnerella dominated polymicrobial adherent biofilms attached to desquamated vaginal epithelial cells.
Results Among the 12 women with BV on urine assessment, 10 had BV according to Nugent’s score and 2 had intermediate microbiota. Presence of Gardnerella in a planktonic mode of growth occurred with 8 women and all have Nugent scores ≤3. Among the 52 women in which no Gardnerella could be documented through FISH, 2 had a Nugent score of ≥ 7, 2 a Nugent score of 4 to 6, and the remainder a Nugent score of ≤ 3. Accordingly, when comparing the FISH based analysis to Nugent scoring, it may be inferred that FISH based analysis has an accuracy for the diagnosis of BV of 0.94 [95% CI 0.86 – 0.98] (sensitivity 0.83 [95% CI 0.51 – 0.97], specificity 0.97 [95% CI 0.87 – 0.99], PPV 0.83 [95% CI 0.51 – 0.97], and NPV 0.97 [95% CI 0.87 – 0.99].
Conclusion Urine-based diagnosis of bacterial vaginosis has a high accuracy. This method is particularly suited for epidemiological and clinical studies as fixated urine sediments can be stored for prolonged periods of time and the aliquots can be used for repeated FISH hybridisations under standardised conditions. In addition, urine samples are easily obtained in a non-invasive manner.
- bacterial vaginosis
- genital microbiome
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