Available guidelines in different countries for routine Group B Streptococcus (GBS) antenatal screening are conflicting. Some recommend routine screening for vaginal and rectal GBS colonization of all pregnant women at 35–37 weeks’ gestation; others recommend no routine screening. According to a 2001 survey, less than 1% of UK maternity units performed routine screening for GBS. Estimates for prevalence of GBS colonization also vary in different countries. The reported rates of prevalence range from 10 to 30%. A similar range was found in the few studies carried out in the United Kingdom and Ireland. It has been suggested that self-collected ano-vaginal swabs for GBS may be as accurate as the current practice of physician-performed swabs.
The aims of this prospective study were to determine the prevalence of ano-vaginal GBS colonization in a cohort of pregnant Irish women, to compare the accuracy of self-collected swabs with that of health professional-collected swabs, and to assess patient preference for the method of swab collection. Six hundred pregnant women at 35–37 weeks’ gestation self-collected an ano-vaginal swab and had a health professional-collected swab on same clinic visit. Their preferences for method of collection were determined by a questionnaire.
The cumulative prevalence of maternal GBS colonization was 11.7% (95% confidence interval [CI], 9.3–14.6), and the sensitivity of the self-collected swab and health professional-collected swab was 84.3% (95% CI, 73.2–91.5) and 94.3% (95% CI, 85.3–98.2), respectively. Despite the excellent concordance in efficacy between the two collection methods, (Kappa = 0.87, P < .001, 97.5% measure of concordance), there was a strong preference among the women (43.2%) for a health-professional to collect their swab. There was less preference (28.5%) for self-collection and 28.3% had no preference.
The close concordance in efficacy between health professional and self-collected swabs could be due in large part to the excellent instruction given to the study subjects on proper sample collection. Such careful instruction may not be possible in a community setting. Despite this possibility, the authors conclude that a patient-collected swab can be a reasonable alternative to a health-professional collected swab.