DNA sequencing of maternal plasma to detect Down syndrome: An international clinical validation study

TLDR

Prenatal screening for Down syndrome has improved, yet invasive diagnostic procedures remain a significant issue, and no prior tests had been performed. The study aimed to assess whether measuring circulating cell‑free DNA in maternal plasma could improve detection of Down syndrome in high‑risk pregnancies. A blinded nested case‑control study of 4,664 high‑risk pregnancies compared fetal karyotyping with a next‑generation sequencing test on maternal plasma, with primary testing at a CLIA‑certified commercial laboratory and cross‑validation by a university laboratory. The test achieved a 98.6 % detection rate, a 0.20 % false‑positive rate, and a 0.8 % failure rate (all euploid), with GC‑content adjustment markedly improving performance, and it can detect nearly all Down‑syndrome cases at a very low false‑positive rate, thereby substantially reducing invasive procedures and fetal loss and supporting clinical implementation.

Abstract

Prenatal screening for Down syndrome has improved, but the number of resulting invasive diagnostic procedures remains problematic. Measurement of circulating cell-free DNA in maternal plasma might offer improvement.A blinded, nested case-control study was designed within a cohort of 4664 pregnancies at high risk for Down syndrome. Fetal karyotyping was compared with an internally validated, laboratory-developed test based on next-generation sequencing in 212 Down syndrome and 1484 matched euploid pregnancies. None had been previously tested. Primary testing occurred at a CLIA-certified commercial laboratory, with cross validation by a CLIA-certified university laboratory.Down syndrome detection rate was 98.6% (209/212), the false-positive rate was 0.20% (3/1471), and the testing failed in 13 pregnancies (0.8%); all were euploid. Before unblinding, the primary testing laboratory also reported multiple alternative interpretations. Adjusting chromosome 21 counts for guanine cytosine base content had the largest impact on improving performance.When applied to high-risk pregnancies, measuring maternal plasma DNA detects nearly all cases of Down syndrome at a very low false-positive rate. This method can substantially reduce the need for invasive diagnostic procedures and attendant procedure-related fetal losses. Although implementation issues need to be addressed, the evidence supports introducing this testing on a clinical basis.