Cell-free DNA screening for fetal aneuploidy using the rolling circle method: A step towards non invasive prenatal testing simplification.

Objective: To assess the efficacy of cell-free (cf)DNA screening for aneuploidy using the automated system based on rolling circle replication. Methods: A prospective study among women referred for invasive prenatal diagnosis between July 2018 and December 2019. The plasma fraction was extracted within 5 days from blood collection, stored at −20°C and cfDNA measured between January and December 2019. Results: A total of 805 women were recruited; 778 with singleton pregnancies and 27 twins. There were 48 Down syndrome, 25 Edwards syndrome and 3 Patau syndrome cases. Overall, the no-call rate was 2.6% (95% confidence interval 1.6%–3.9%) which reduced from 4.7% to 1.1% after relocation of the system (p < 0.002) to ensure a constant ambient temperature below 25°C. In singletons the Down syndrome detection rate (DR) was 100% (93%–100%) and false-positive rate (FPR) 0.14% (0.00%–0.79%). The Edwards syndrome DR was 96% (80%–100%) and FPR 0.78% (0.29%–1.7%). One false-positive had a confined placental trisomy 18 and the remaining five a z-score requiring sample repetition; all the false-positives occurred before system relocation (p < 0.005). Patau syndrome DR and FPR were 67% (9.4%–99%) and 0.26% (0.03%–0.95%). Conclusion: The cfDNA rolling circle method yields similar results to other methods provided that room temperature is adequately controlled.