The accuracy of various tests for bacterial vaginosis in predicting preterm birth: a systematic review

To determine the accuracy with which various types of tests for bacterial vaginosis predict spontaneous preterm birth in pregnant women.

Studies were identified without language restrictions through nine different databases, and manual searching of bibliographies of known primary and review articles.

There are four different bacterial vaginosis testing methods: Gram staining tests using either Nugent's or Spiegel's criteria, and gas liquid chromatography are laboratory based, and the fourth method uses clinical (Amsel's) criteria to diagnose bacterial vaginosis. Two reviewers independently selected studies and extracted data on their characteristics, quality and accuracy. Accuracy data were used to form 2 x 2 contingency tables of the bacterial vaginosis test results with spontaneous preterm birth as the reference standard.

Data on asymptomatic women and women with symptoms of threatened preterm labour were analysed separately. Data were pooled to produce summary estimates of likelihood ratios for positive (LR+) and negative (LR-) test results for the various types of tests.

There were 18 primary articles, involving altogether 17,868 women. There was unexplained heterogeneity in the meta-analyses of the accuracy results, which requires caution in their interpretation. Meta-analyses of studies testing asymptomatic women in the second trimester showed that clinical criteria had a LR+ of 0.98 (95% confidence interval 0.59 to 1.6) and a LR- of 1.00 (0.93 to 1.1), Gram staining (Nugent's criteria) had a LR+ of 1.6 (1.4 to 1.9) and a LR- of 0.9 (0.8 to 0.9), and Gram staining (Spiegel's criteria) had a LR+ of 2.4 (1.4 to 4.9) and a LR- of 0.81 (0.64 to 1.0). Among symptomatic women, Gram staining (Spiegel's criteria) had a LR+ of 1.3 (1.0 to 1.6) and LR- of 0.9 (0.7 to 1.0).

There was a lack of difference in the accuracy of the various bacterial vaginosis tests for predicting preterm birth in both asymptomatic and symptomatic women of threatened preterm labour.