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

Abstract

Objective To determine the accuracy with which various types of tests for bacterial vaginosis predict spontaneous preterm birth in pregnant women. Data sources Studies were identified without language restrictions through nine different databases, and manual searching of bibliographies of known primary and review articles. Study selection and data extraction 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 Â 2 contingency tables of the bacterial vaginosis test results with spontaneous preterm birth as the reference standard. Data synthesis 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 (LRþ) and negative (LRÀ) test results for the various types of tests. Results 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 LRþ of 0.98 (95% confidence interval 0.59 to 1.6) and a LRÀ of 1.00 (0.93 to 1.1), Gram staining (Nugent's criteria) had a LRþ of 1.6 (1.4 to 1.9) and a LRÀ of 0.9 (0.8 to 0.9), and Gram staining (Spiegel's criteria) had a LRþ of 2.4 (1.4 to 4.9) and a LRÀ of 0.81 (0.64 to 1.0). Among symptomatic women, Gram staining (Spiegel's criteria) had a LRþ of 1.3 (1.0 to 1.6) and LRÀ of 0.9 (0.7 to 1.0). Conclusion 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.

Likelihood ratios for the prediction of preterm delivery with biomarkers

“…Bacterial vaginosis diagnosed according to Nugent's criteria provided an LR+ of 1.6 (20) (number of screen‐positive PTD >100), and vaginal carriage of group B streptococci was not associated with PTD (21) (number of screen‐positive PTD 50–100). Based on one small study, the finding of Ureaplasma urealyticum in amniotic fluid had an LR+ of 10.…”

Biomarkers for the prediction of preterm delivery

“…A Swedish study found comparable results (LR+ of 7, SENS 35%, and FP 5%) for predicting PTD before 34 weeks (7). The association of BV with PTD is well documented, and the pooled LR+ estimate was 1.3 (1.0–1.6) in a metaanalysis on 575 subjects using Spiegel's criteria (8).…”

Bacterial vaginosis Transmission, role in genital tract infection and pregnancy outcome: an enigma

“…Another recently published meta‐analysis studied the accuracy of different tests for BV when predicting preterm birth (36). Studies testing asymptomatic women in the second trimester showed that clinical criteria had a likelihood ratio (LR) of 0.98 (95% CI 0.59 to 1.6) and an LR‐ of 1.00 (0.93 to 1.1), Gram‐staining (Nugent's criteria) had an LR+ of 1.6 (1.4 to 1.9) and an LR‐ of 0.9 (0.8 to 0.9), and Gram‐staining (Spiegel's criteria) had an LR+ of 2.4 (1.4 to 4.9) and an LR‐ of 0.81 (0.64 to 1.0).…”