Oral or Poster Presentation
Concurrent Session 4C - Reproductive Science
Introduction: In Ontario, prenatal screening for aneuploidy is offered in the form of a mixed-contingent model, in which multiple marker screening (MMS) is offered to all pregnant individuals and cell-free DNA (cfDNA) screening is funded as a first-tier screen if specific eligibility criteria are met, or as a contingent test after a screen positive MMS result.
Prenatal Screening Ontario (PSO), housed within the Better Outcomes Registry & Network (BORN) Ontario, was established by the province’s Ministry of Health in 2017 with the mandate to coordinate the operations of prenatal screening services. To ensure optimal functioning of the system of care, it is essential to understand the performance of the current provincial screening system. The objective of this study was to assess screening performance in the Ontario population.
Methods: This descriptive cohort study was based on secondary analyses of data collected by BORN Ontario. The study population included all singleton pregnancies with an estimated date of delivery (EDD) from September 1, 2016 to August 31, 2018.
Results: There were 290,518 singleton pregnancies within the EDD date range. Of those, 191,981 (66.0%) received MMS, and 16,479 (5.7%) received publicly-funded cfDNA screening. The overall MMS detection rate (DR) for trisomy 21 (T21) combining all screening modalities was 87.98%, (95% CI: 84.58,90.87), with a false positive rate (FPR) of 4.61% (4.52,4.71). For cfDNA screening, T21 screening DR was 100.00% (98.88,100.00), with a FPR of 0.19% (0.13,0.28). Overall, Ontario’s screening system demonstrated a DR of 92.02% (89.36,94.18) for T21 at a FPR of 4.54 % (4.44,4.63), DR for trisomy 18 was 86.99% (80.43,91.98) at an FPR of 0.24% (0.22,0.26).
Conclusion: This study is the first look at the overall performance of prenatal screening for aneuploidy in Ontario, a unique mixed-contingent system. Future studies will use registry data to evaluate algorithm options to optimize screening performance and cost-efficiency.