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

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.

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).

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.

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.