Evaluation of a rapid latex agglutination test for detection of group B streptococci in vaginal specimens

Abstract

A rapid latex agglutination test (Bactigen Group B Streptococcus Cervical Screen) for detection of group B streptococci in cervical-vaginal specimens was evaluated using two different slide systems, the traditional serologic slide and capillary action track (Trak) slide. Culture was used as reference method. A total of 344 cervical-vaginal specimens were tested. The group B streptococci carrier rate was found by culture to be 10.8%, 56.8% of these specimens being heavily colonized. The sensitivity and specificity of the latex agglutination test in heavily colonized specimens was 95.2% and 99.3% for the serologic and track slides respectively. The overall sensitivity, including lightly colonized specimens, was 62.2%. The positive predictive value was 92% for both slide systems, and the negative predictive value 95.4% and 95.6% for the serologic and track slides respectively. The latex agglutination test, used with either slide, provides a rapid and effective method for identification of specimens heavily colonized with group B streptococci. The track slide may provide a convenient alternative to serologic slides since it does not require rotation.

Evaluation of chromogenic medium and direct latex agglutination test for detection of group B streptococcus in vaginal specimens from pregnant women in Lebanon and Kuwait

“…per swab) women, presenting the sensitivity and specificity of 63 and 99.7 %, respectively (Kontnick & Edberg, 2002). In two other analogous studies, sensitivity and specificity were reported as 85.7 and 99.3 %, respectively, by Wald et al (1987) and 95.2 and 99.3 %, respectively, by Lotz-Nolan et al (1989). In both these studies, a different method of antigen extraction, viz.…”

Direct detection of group B streptococci from vaginal specimens compared with quantitative culture

“…The results reported here with LPA-enzyme extraction (Streptex) demonstrated a sensitivity and a specificity in a heavily colonized population of 63 and 99.7%, respectively, analogous to the values found by Wald et al (25) (sensitivity and specificity, 85.7 and 99.3%, respectively). Lotz-Nolan et al (21) found a sensitivity and a specificity of 95.2 and 99.3%, respectively. Both of these studies, done with micronitrous acid extraction, demonstrated a better sensitivity than that found here.…”

“…Alternatively, the results reported here may be more reflective of the actual clinical situation, taking into account variations in collection, transportation, etc. (the study by Lotz-Nolan et al [21] was not performed under clinical conditions). All three studies had very similar specificities, indicating very few problems with other microbes producing false-positive results.…”

“…Their study demonstrated that it was possible to directly detect GBS antigen from clinical vaginal specimens. Wald et al (25) and Lotz-Nolan et al (21) also used micronitrous acid extraction with latex agglutination to detect GBS antigen directly from vaginal swabs. Data gathered from the above-mentioned studies also indicate that latex agglutination-direct antigen extraction could be a rapid, sensitive method for the detection of GBS, particularly for high-risk, heavily colonized women.…”

“…Of particular concern was the observation that specimens from three heavily colonized women (>106 CFU per swab) yielded false-negative results. Two recent studies by Wald et al (25) and Lotz-Nolan et al (21) focused on heavy colonization (3+ to 4+) as well. Both studies used a semiquantitative culture and LPA-micronitrous acid extraction (Bactigen; Wampole Laboratories, Cranbury, N.J.).…”