The accuracy and influencing factors for preference of self-sampling in group B streptococcus screening: a cross-sectional study

Background: Self-sampling with proper instruction in 35-37 weeks’ gestation is supplementary to clinician sampling to prevent early-onset invasive group B streptococcal disease of infants. Despite of the accuracy proved in previous studies, disputes were raised on pregnant women’s low preference and adherence to the method of swab collection. We aimed to assess the accuracy of self-sampling and influencing factors for preference on collection method in Chinese women. Methods We compared screening results of self-sampling with clinician collection in a sample of 522 women in late pregnancy. These participants needed to complete a questionnaire on their preference and demographics after self-sampling. A multi-nominal logistic regression model was then used to measure the association between the influencing factors and preference for collection method. Results A good agreement between the two collection methods was found with a Cohen’s Kappa coefficient 0.83 (95%CI 0.71-0.95). The prevalence of GBS infection in the two methods is statistically different. Four factors (maternal age, parity, education attainment and pain difference) were included in the final multi-nominal regression model while gestational age and vaginal suppository use were excluded. Non-elderly parturient women were 2.84 (95% CI 1.19-6.74) times more likely to prefer self-sampling compared to clinician sampling, adjusting for parity, education and pain difference. If these participants experienced more or equal pain during self-sampling compared to clinician collection, they were more likely to prefer clinician sampling controlling the other three factors’ effect. Conclusions Our study suggests high agreement between the two collection methods. Self-sampling presented a higher detection rate than physician-collected samples. Pregnant women are able to collect rectovaginal samples prior to their antenatal visit. Self-sampling is preferable by 1/5 of the participants and it could be an option for those younger than 35 years old, especially for those with low pain threshold.