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

Objective: Self-sampling with proper instruction in 35-37 weeks' gestation is an option to clinician sampling to prevent early-onset invasive group B streptococcal disease of infants. We aimed to assess the accuracy of self-sampling and influencing factors of preference for collection method in Chinese women.

Methods: We compared the screening results of self-sampling with clinician collection in a sample of 520 women in late pregnancy. We collected their demographics, clinical information and preference for collection method. A multi-nominal logistic regression model was used to measure the association between the influencing factors and these participants' preference.

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 in this low-risk group when self-sampling presented a better outcome in terms of detecting positive cases. Self-sampling is preferable by 20.9% of the participants. No less pain during self-sampling and age older than 35 years old was statistically related to preference for clinician collection.

Conclusion: The accuracy of self-sampling is no worse than clinician collection. It could be an option for those younger than 35 years old, especially for those who report low pain threshold. Pregnant women are able to collect rectovaginal samples prior to their antenatal visit. Self-sampling followed by appropriate transportation of the sample to an advanced laboratory could eliminate the effects of local laboratory capacity. There are implications in increasing GBS screening participation in resource-limited settings.