Bacterial vaginosis diagnosed by analysis of first-void-urine specimens

Abstract

Bacterial vaginosis (BV) is traditionally diagnosed using vaginal samples. The aim of this study was to investigate whether BV can be diagnosed from first-void urine (FVU). Self-collected vaginal smears, vaginal swabs, and FVU were obtained from 176 women. BV was diagnosed by Nugent's criteria. The FVU and vaginal swabs were analyzed by quantitative PCRs (qPCRs) for selected vaginal bacteria (Atopobium vaginae, Prevotella spp., Gardnerella vaginalis, bacterial vaginosis-associated bacterium 2, Eggerthella-like bacterium, "Leptotrichia amnionii," Megasphaera type 1), and all had an area under the receiver operating characteristic (ROC) curve of >85%, suggesting good prediction of BV according to the Nugent score. All seven bacteria in FVU were significantly associated with BV in univariate analysis. An accurate diagnosis of BV from urine was obtained in this population by a combination of qPCRs for Megasphaera type 1 and Prevotella spp. The same two bacteria remained significantly associated with BV in a multivariate model after adjusting for the other five species. There was no statistically significant difference between the sensitivities and specificities of BV diagnosis by molecular methods performed on swabs and FVU samples. A linear regression analysis showed good agreement between bacterial loads from swabs and FVU, but Prevotella spp. could be detected in high numbers in a few FVU samples without being present in swabs. This method will allow diagnosis of BV in studies where only urine has been collected and where detection of BV is considered relevant.

FIG 1

Bacterial load in swabs and urine samples from 73 women with a normal flora, 25 women with an intermediate flora, and 78 women with BV as diagnosed from Nugent's score. The median bacterial load is marked with a horizontal bar for each group.

FIG 2

Correlation between the bacterial load in swabs and urine samples. For each bacterium a regression line for the correlation between the log₁₀ of 16S rRNA gene copies per ml + 1 in swabs versus FVU is shown. Nugent grades of vaginal smears are shown in color. The lower right graph shows the 7 regression lines in the same graph for easier comparison.

FIG 3

Hierarchically clustered Spearman correlation coefficients between bacterial species in urine showing cooccurrence of species. Correlation coefficients range from 0.57 to 1. A table with the coefficients is available (see Data Set S2 in the supplemental material).