An enrichment method to increase cell-free fetal DNA fraction and significantly reduce false negatives and test failures for non-invasive prenatal screening: a feasibility study

Table 2 Performance of NIPS using cffDNA enrichment on 11 false negative samples

No.	Karyotype	NIPS without cffDNA enrichment		NIPS with cffDNA enrichment
No.	Karyotype	Fetal fraction (%)	Z score	Fetal fraction (%)	Z score
FN1	47,XX,+ 21	5.6	2.41	15.6	11.92^a
FN2	47,XY,+ 18	8.5	− 0.41	18.6	− 1.05
FN3	47,XX,+ 21	4.8	1.14	11.4	5.076^a
FN4	47,XY,+ 21	12.4	0.791	26.4	2.16
FN5	47,XY,+ 18	7.1	0.313	15.2	1.687
FN6	47,XY,+ 18	5.1	1.713	11.8	4.01^a
FN7	47,XY,+ 21	11.2	0.163	18.8	− 1.86
FN8	47,XY,+ 21	9.2	− 0.56	19	1.096
FN9	47,XY,+ 21	7.5	− 0.16	14.7	1.634
FN10	47,XY,+ 21	6.4	2.031	14.6	10.14^a
FN11	47,XY,+ 21	4.1	1.255	7.9	6.972^a

NIPS noninvasive prenatal screening, cffDNA cell-free fetal DNA, FN false negative
^aPositive results using cffDNA enrichment method

ISSN: 1479-5876