Comparison of Culture and Rapid Enzyme Immunoassay for the Detection of Group B Streptococcus in High-Risk Pregnancies

OBJECTIVE The purpose of this study was to evaluate the Equate Strep B(R) test for clinical use in patients at high risk for complications from group B streptococcus (GBS) disease. METHODS Vaginoperineal swabs were obtained from patients with preterm premature rupture of the membranes and/or preterm labor and semiquantitative GBS cultures and Equate(R) assay were performed. RESULTS From May 14, 1990, to April 30, 1992, 650 patients were enrolled; 626 had both culture and Equate(R) results available, of whom 24% were colonized with GBS. The sensitivity, specificity, positive predictive value, and negative predictive value of the rapid assay were 28%, 84%, 35%, and 79%, respectively. Although the prevalence of GBS was higher in patients with ruptured membranes compared with those with intact membranes, rupture of membranes did not affect test sensitivity or specificity. CONCLUSIONS We conclude that the Equate(R) rapid assay is not a sensitive method of GBS detection in high-risk patients.