Date of Award

January 2020

Document Type


Degree Name

Medical Doctor (MD)



First Advisor

Jessica Illuzzi

Second Advisor

Seth Guller


While great progress has been made to reduce its incidence, group B streptococcus (GBS) is still a leading cause of neonatal disease. Current standard of care recommends antepartum rectovaginal GBS culture of all pregnant women at 36 weeks of gestation in order to identify candidates for intrapartum prophylaxis to reduce vertical transmission. The purpose of the study is to assess three alternative nucleic acid amplification (NAAT) screening strategies for GBS: antepartum NAAT at 36 weeks, intrapartum NAAT, or a combined intrapartum and antepartum approach in which patients with penicillin allergies undergo antepartum culture screening and all other patients undergo intrapartum NAAT screening. A decision tree model was created using TreeAge Pro Suite 2018 where values of input parameters (probabilities, costs, and utilities) were obtained from published literature. All cost estimates were reported in 2019 U.S. dollars. Base case analysis, one-way sensitivity analyses, and a Monte Carlo simulation were conducted to assess the cost-effectiveness of NAAT at 36 weeks, intrapartum NAAT, and combined intrapartum/antepartum screening, relative to antepartum culture screening at 36 weeks. An incremental cost-effectiveness ratio (ICER) below $100,000 per quality-adjusted life year (QALY) was considered cost-effective. The base case analysis showed that, among the three proposed NAAT strategies, the combined antepartum and intrapartum approach as well as the intrapartum approach are cost-effective, with an ICER of $92,109.56 per QALY and $97,791.02 per QALY, respectively, compared to antepartum culture based screening. One way sensitivity analysis showed that the intrapartum NAAT approach was more favorable than antepartum culture when the GBS carrier prevalence was below 22%, the percentage of women who changed GBS carrier status from negative to positive (negative to positive conversion rate) was above 3.8% and the intrapartum NAAT error rate was less than 5%. The Monte Carlo simulation showed that the combined approach was the optimal strategy in 49% of iterations while antepartum culture was the optimal approach in 51% of iterations. Cost-effectiveness acceptability curve showed that the combined approach had a 0.48 probability of being cost effective compared to antepartum culture at a willingness-to-pay (WTP) threshold of $100,000 per QALY. Intrapartum screening methods involving NAAT could potentially be cost-effective interventions to reduce the morbidity and mortality of GBS disease. Given limited data about the efficacy of clindamycin and vancomycin in women with anaphylactic penicillin allergy, further study is required to determine the optimal strategy to reduce early onset GBS sepsis of the newborn.


This thesis is restricted to Yale network users only. It will be made publicly available on 09/10/2022