High-throughput fetal-fraction amplification increases analytical performance of noninvasive prenatal screening

ABSTRACT Purpose The percentage of a maternal cell-free DNA (cfDNA) sample that is fetal-derived (the fetal fraction; FF) is a key driver of the sensitivity and specificity of noninvasive prenatal screening (NIPS). On certain NIPS platforms, >20% of women with high body-mass index (and >5% overall) receive a test failure due to low FF (<4%). Methods A scalable fetal-fraction amplification (FFA) technology was analytically validated on 1,264 samples undergoing whole-genome sequencing (WGS)-based NIPS. All samples were tested with and without FFA. Results Zero samples had FF<4% when screened with FFA, whereas 1 in 25 of these same patients had FF<4% without FFA. The average increase in FF was 3.9-fold for samples with low FF (2.3-fold overall) and 99.8% had higher FF with FFA. For all abnormalities screened on NIPS, z-scores increased 2.2-fold on average in positive samples and remained unchanged in negative samples, powering an increase in NIPS sensitivity and specificity. Conclusions FFA transforms low-FF samples into high-FF samples. By combining FFA with WGS-based NIPS, a single round of NIPS can provide nearly all women with confident results about the broad range of potential fetal chromosomal abnormalities across the genome.