Rapid Test Validated for Group B Streptococcus

A rapid laboratory test that detects potentially deadly Group B Streptococcus (GBS) has been successful at identifying GBS colonization in pregnant women in six and a half hours.

The expeditious test could be helpful for the 13% of patients who experience preterm labor before they are screened for GBS, which usually occurs between 35 and 37 weeks of gestation, and normally must wait at least 48 hours before the bacteria is identified.

In a study carried out at the University of Texas (Houston, TX, USA) enrolled 356 patients at 35 to 37 weeks of gestation who were tested for GBS using two standard tests and the new test, which provided a high level of validity according to the study results. The mean gestational age at study enrollment was 35.6 weeks of gestation and the mean age of women was 26.8 ± 0.6 years.

Three vaginal-rectal swabs were collected per patient; two were processed by traditional culture, commercial laboratory versus in-house culture, and the third was processed by an immunoblot-based test. In the latter test, a sample is placed over an antibody-coated nitrocellulose membrane, and after a six-hour culture, bound GBS is detected with a secondary antibody. The third swab was processed by the antibody-based accelerated QuickTest (Nanologix, Inc.; Hubbard, OH, USA).

In this study of diagnostic accuracy, the accelerated GBS test demonstrated a high level of sensitivity and specificity for the detection of antepartum GBS within 6.5 hours and a substantial agreement between observers. The new test can also detect antibiotic sensitivities for women, who are allergic to penicillin, saving the additional 48 hours the standard test for antibiotic sensitivity takes. The rapid test detected 131/356 (36.8%) GBS in the patients compared to 105 (29.5%) from the in-house culture, and 84 (23.6%) from the commercial culture.

Jonathan Faro, MD, PhD, the lead author, said, "This new test could change the management of patients who present to labor and delivery with threatened preterm labor and are not expected to deliver right away. Everyone is concerned that the overuse of antibiotics is leading to greater resistance to them. Some have expressed concern that by giving penicillin to everyone, we are increasing the number of babies who are getting sick from Escherichia coli sepsis." The study was accepted for publication on January 13, 2013, in the journal Infectious Diseases in Obstetrics and Gynecology.

Related Links:
University of Texas
Nanologix, Inc.