Vaginal-perianal compared with vaginal-rectal cultures for detecting group B streptococci during pregnancy

To estimate whether vaginal-perianal cultures could be an alternative to the recommended vaginal-rectal screening cultures for the detection of group B streptococci (GBS) during pregnancy, and to compare patient pain and discomfort between the two collection methods.

Patients included were aged 18 or older and at 35-37 weeks of gestation. After consent, each patient underwent collection of a vaginal-perianal followed by a vaginal-rectal culture. Patients rated their pain on a 0-to-10 scale for each collection method and indicated whether one method had more discomfort than the other. The primary outcome of the study was the proportion of patients whose vaginal-perianal and vaginal-rectal culture results agreed with one another.

Data were collected from 193 patients. The overall agreement rate between the vaginal-perianal and vaginal-rectal cultures was 186 out of 193 (96.4%; lower 95% confidence bound was 93.4%), yielding a 91.1% sensitivity and 98.5% specificity. There were two false positives and five false negatives. The GBS detection rates were similar between the two collection methods (P = .257). On average, pain was 3.4 points for the vaginal-rectal method and 1.2 points for the vaginal-perianal method (P<.001). More than two-thirds of the patients stated that the vaginal-perianal collection method had less discomfort than the vaginal-rectal method.

Agreement was high between the recommended vaginal-rectal and the studied vaginal-perianal collection methods. Patients indicated less pain and discomfort with the vaginal-perianal collection method. Therefore, vaginal-perianal cultures may be reasonable, patient-preferred alternatives for the recommended vaginal-rectal cultures for detection of GBS during pregnancy.

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