853: The cost effectiveness of multiple GBS screening intervals

Abstract

Group B streptococcus (GBS) is the leading causative agent of neonatal sepsis in the United States. As such, the CDC recommends a single GBS screening in the form of rectovaginal culture at 35-37 weeks gestation to determine use of maternal intrapartum antibiotic prophylaxis (IAP) to prevent perinatal transmission. However, prediction of perinatal transmission is complicated by the conversion of some women to GBS-positive status prior to delivery, despite a negative initial test result. This study set out to evaluate the use of repeat screening at varying weekly intervals as a cost-effective strategy to decrease rates of GBS transmission to neonates and subsequent outcomes. A decision-analytic model was created using TreeAgePro and probabilities, costs, and utilities derived from the literature. The screening strategies compared included: the usual care of no repeat screening; one additional test at 39, 40, or 41 weeks gestation; every other week testing beginning at 38 weeks; or weekly testing beginning at 37 weeks. This model was then applied to a theoretical cohort of 1,800,000 women based on the estimated number of nulliparous, term-births annually in the United States. The cost-effectiveness threshold was set at $100,000 per quality-adjusted life year (QALY). Univariate sensitivity analyses were performed to evaluate the robustness of the results. In our model, at baseline assumptions of antepartum culture sensitivity of 97% when compared to intrapartum culture, a single repeat screen at 41 weeks was the cost-effective strategy. This persisted to culture sensitivity as low as 94.6% and culture cost ranging from $14 to $44. When compared to no retesting, a single retest at 41 weeks yielded 1.1 fewer neonatal deaths at a cost of $2.7 million. However, weekly testing resulted in 5 fewer neonatal deaths at a cost of $120 million when compared to no repeat testing (Table 1). Repeat antepartum GBS screening at 41 weeks compared to usual care is a cost-effective strategy. Rescreening at 41 weeks appears to be cost effective at a variety of hypothetical culture sensitivities and costs. Repeat antepartum screening should be considered in the management of women with initial GBS negative screening.