(417) Indication for Invasive Testing in the Age of Expanded Carrier Screening

Expanded carrier screening is widely available and offers testing for > 500 conditions. Most individuals screened will be identified as having one or more carrier states. While the frequency of carrier couples would be expected to rise, the impact on diagnostic testing via CVS or amniocentesis is unknown. Our objective was to explore the relationship between utilization of expanded carrier screening and the indications for diagnostic testing.

Study Design:

This was a retrospective cohort study at a tertiary care center from 2016-2021 where expanded carrier screening was made available in 2016. All pregnant patients undergoing invasive testing were included. Patients with incomplete or missing data were excluded. Comparison over 3 periods (2016-17, 2018-19, and 2020-21) was performed. Analysis was done using Chi-square analysis.

Results:

436 patients met inclusion criteria. 81% of patients were ≥ 35 years at time of delivery and 21.3% conceived via IVF.

The proportion of those who underwent expanded carrier screening significantly increased over the study periods (Table 1). The distribution of indications for invasive testing also changed, with a significant increase in positive carrier testing as the indication for diagnostic testing: 2.8%, 8.1%, and 14.4%, respectively (p = < 0.001).  Mutations for Familial Mediterranean Fever (13.5%) and Alpha Thalassemia (10.8%), were those most commonly tested (Table 2). There were no significant differences in age, race, insurance type or mode of conception across the study periods.

Conclusion:

Expanded carrier screening and diagnostic testing for the indication of positive carrier status rose significantly between 2016 and 2021. While “Advanced Maternal Age” remained the most common single indication, diagnostic testing for single gene disorders may displace this as expanded carrier screening becomes more common. As physicians become more familiar with those conditions with relatively high carrier frequencies, invasive testing may be reserved for those conditions with more severe phenotypes.