902: Cell-free DNA for Down syndrome screening in morbidly obese women: Is it a cost-effective strategy?

Abstract

Cell-free DNA (CfDNA) screening in morbidly obese (body mass index ≥ 40 kg/m2) women has an increased no result rate due to lower fetal fraction. Conventional serum screening is not limited by maternal weight. The aim of this project was to estimate the cost-effectiveness of trisomy 21 (T21) screening in morbidly obese women using cfDNA compared to traditional serum integrated screening. Using TreeAge software, we created a decision-analytic model to compare two prenatal screening strategies for fetal trisomy 21 detection: (1) Serum integrated screening (INT) with first trimester PAPP-A and beta-hCG and second trimester quad screen and (2) cfDNA screening. We performed a literature review to model rates of insufficient fetal fraction, invasive testing for abnormal results, test performance characteristics, incidence of T21, rates of live birth, termination, and stillbirth in each clinical scenario. Costs of screening, invasive testing, termination, procedure- related fetal loss and of a T21 live birth were obtained from literature review. Primary outcomes of the model were the cost of each strategy, number of unnecessary invasive tests, procedure-related fetal losses, and missed cases of T21. In the base case, the mean cost of cfDNA was $453 greater than that of INT ($1,310 vs $857). cfDNA resulted in a lower probability of an unnecessary invasive test (2.9% vs 3.7%), procedure-related fetal loss (0.015% vs 0.019%), and missed cases of T21 (0.00013% vs 0.02%), respectively. cfDNA cost $56,000 per unnecessary invasive test avoided, $11 million per procedure-related fetal loss avoided, and $2 million per missed case of T21 avoided. In sensitivity analysis, when the probability of an insufficient fetal fraction is assumed to be > 25%, cfDNA is both costlier than INT and results in more unnecessary invasive testing (a dominant strategy). When compared to serum integrated screening, cfDNA is costlier and results in higher rates of unnecessary invasive testing in morbidly obese women with a probability of insufficient fetal fraction > 25%, which occurs at a maternal weight of approximately ≥300 pounds.