Impact of observed versus hypothesized service utilization on the incremental cost of first trimester screening and prenatal diagnosis for trisomy 21 in a Canadian province

OBJECTIVE: The aim of this research was to determine the impact of observed versus hypothesized service utilization on the cost of first trimester screening (FTS) and prenatal diagnosis for trisomy 21 in a Canadian province. METHODS: A population-based pregnancy cohort was created by linking 12 clinical and administrative databases. Care trajectories were derived to examine utilization patterns for FTS, prenatal diagnosis, and pregnancy termination. A literature review was conducted to determine what utilization parameters were used in economic evaluations of FTS. Local cost data was applied to observed and hypothesized care trajectories. RESULTS: The observed mean cost per fetus with trisomy 21 detected prenatally using FTS was $129,606.04 compared with $27,021.45 for women who did not access FTS. Observed utilization of FTS and prenatal diagnosis among screen positive women and termination of pregnancy following prenatal diagnosis of trisomy 21 were substantially lower than hypothesized in existing cost effectiveness studies. Cost estimates were sensitive to hypothetical changes in utilization of prenatal screening, prenatal diagnosis, and pregnancy termination. CONCLUSION: Literature-based estimates of the cost-effectiveness of prenatal screening may not accurately represent current local practice due to potentially unrealistic assumptions about what proportion of women will proceed to invasive testing and ultimately terminate an affected pregnancy.