Accuracy of an Accelerated, Culture-Based Assay for Detection of Group B Streptococcus

Abstract EN

Objective.

To determine the validity of a novel Group B Streptococcus (GBS) diagnostic assay for the detection of GBS in antepartum patients.

Study Design.

Women were screened for GBS colonization at 35 to 37 weeks of gestation.

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 which a sample is placed over an antibody-coated nitrocellulose membrane, and after a six-hour culture, bound GBS is detected with a secondary antibody.

Results.

356 patients were evaluated.

Commercial processing revealed a GBS prevalence rate of 85/356 (23.6%).

In-house culture provided a prevalence rate of 105/356 (29.5%).

When the accelerated GBS test result was compared to the in-house GBS culture, it demonstrated a sensitivity of 97.1% and a specificity of 88.4%.

Interobserver reliability for the novel GBS test was 88.2%.

Conclusions.

The accelerated GBS test provides a high level of validity for the detection of GBS colonization in antepartum patients within 6.5 hours and demonstrates a substantial agreement between observers.