The Accuracy of Self-Screening of Group B Streptococcus in Pregnant Women—A Randomized Crossover Study

Abstract

Objective: Universal screening of vaginal and rectal group B streptococcus (GBS) carriage in pregnant women is now recommended in many countries to identify at-risk pregnancies and reduce the risk of early-onset GBS disease in newborn infants. This study compared self-screening by pregnant women with screening by health care workers in a largely Chinese population.

Methods: A randomized crossover study was conducted in Hong Kong. All women attending the GBS screening visit at 35–37 weeks gestation between May and October 2015 were approached for recruitment. Consenting participants underwent both self-screening and screening by health care workers. Group 1 had health care worker screening swabs first, and group 2 had self-screening first. A positive GBS diagnosis was made if either swab was positive. The sensitivity of each approach was calculated by comparison with this gold standard. Acceptance of GBS self-screening and neonatal outcomes was analyzed (Canadian Task Force Classification I).

Results: Of the 672 women approached, 428 (63.7%) consented to the study. The prevalence of GBS was 19.7% (83 of 422). Sensitivities of self-screening and screening by health care workers were 61.4% (51 of 83) and 97.6% (81 of 83), respectively (P < 0.05). Women who used vaginal pessaries and non-Chinese women had a higher positive concordance rate with health care workers (P < 0.05). Neonatal outcomes of GBS-positive mothers were similar in the concordant and discordant groups.

Conclusion: The sensitivity of self-screening of GBS in Hong Kong was lower than the sensitivity of screening by health care workers. Cultural difference needs to be considered when implementing self-screening in different populations.