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CME Credit Offered
CME Credit Offered
Abstract Award
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Poster Session 4

(1183) Monogeneic Disorder (MD) Screening using Cell-Free DNA (cfDNA) In Routine Practice

Friday, January 31, 2025
4:00 PM – 6:00 PM  
Objective: More pregnancies are affected by MDs than by trisomy 21. MDs are often not identified on ultrasound, standard invasive testing, or microarray. Clinical studies of cfDNA detection of MD report >99% sensitivity and specificity, with a 1:600 incidence of positive results in a high-risk population. We sought to determine (1) the feasibility of offering routine cfDNA for MD, (2) false positive rate of MD diagnosed at the time of cfDNA for aneuploidy, (3) accuracy of cfDNA for MD when routinely offered to low-risk patients.

Study Design: From 10/11/2021-7/15/2024 all patients in a single obstetrical practice were offered MD screening (25 conditions in 47 genes) at the time of cfDNA screening for aneuploidy. Patients with egg donors, multiple gestation, and vanishing twins were excluded, as were those who had testing for ultrasound findings or other risk factors. Genetic counseling, diagnostic CVS/amniocentesis, and parental testing were recommended for patients with positive results. Repeat testing was recommended for patients who did not receive a result.

Results:

1831 pregnancies in 1746 women were included. Results were positive in 5 pregnancies (0.28%) (Table), negative in 1730 (94%), and 96 (5.2%) received no initial result. 75/96 patients repeated testing: 63 were negative and 12 did not result (0.66% final no-call rate). Of the positive tests, 4 were true positive on confirmatory testing with CVS or amniocentesis and one was negative for both fetus and parents. MD testing was positive in 1:366 patients; incidence of the disorders was 1:458. False positive results occurred in < 1% of tests.

Conclusion: MDs affected >1:500 pregnancies. Screening for MDs is not recommended by professional societies or offered as part of routine care. Screening for MD in low-risk pregnancies is feasible. MD screening in the general population should be considered, as it is unlikely to significantly increase unnecessary invasive testing and may prenatally diagnose conditions and afford women reproductive choice in the current pregnancy and the future.