Evaluation in rural practice of a rapid group B streptococcus screening test

Group B streptococcus (GBS) is the leading cause of infant mortality from infection. A rapid screening immunoassay for GBS was evaluated in a rural obstetrical population and was found to have an unacceptably low specificity (90%) and sensitivity (50%). With a culture proven GBS colonization rate of 6.8%, the positive predictive value of the rapid screening test was only 27%, and the negative predictive value was 96%. Current recommendations for routine vaginal cultures, on all women based on urban research data with high maternal colonization rates (15%-23%) and high prematurity rates (15%-40%) are reviewed in relation to this community's low colonization and prematurity rates.