Reliability of a rapid latex fixation test for detecting group B streptococci in the genital tract of parturients at term.

The purpose of this prospective investigation was to determine the reliability of a rapid latex particle agglutination test in detecting group B streptococci in the lower genital tract of laboring women. Five hundred asymptomatic patients with intact membranes who were in labor at term underwent sterile speculum examination. Secretions from the endocervix and vagina were collected with sterile swabs. One swab was inoculated directly onto a blood agar plate for culture. The other was initially placed into a Culturette transport system and then transferred into a test tube containing an enzyme extraction reagent. After a 60-minute incubation at 37C, the latex fixation test was performed on the residual liquid in the tube. The frequency of positive cultures in our population was 5.0%. The sensitivity and specificity of the rapid slide test were 88 and 99.6%, respectively. The positive and negative predictive values were 91.7 and 99.4%, respectively. The group B streptococci latex fixation test appears to be a rapid and reliable means of detecting group B streptococci in the lower genital tract of term patients with intact membranes. Use of this method should permit a more selective approach to the intrapartum chemoprophylaxis of women colonized with group B streptococci.