Fig. 1
The copy number ratio (R) between Chromosome 21 (Chr21) and Chromosome 18 (Chr18) (R21/18) without and with 7 cycles of pre-amplification (PA) before the dPCR-NIPT assay, in which 8 µL of 12.5 fold-diluted PA product was used. A R21/18 of 16 individual euploid plasma samples without (blue solid bars) and with (red solid bars) PA. B Mean R21/18 of the 16 euploid samples without (blue right slash lines) and with (red left slash lines) PA valued at 0.9901 with a SD of 0.0175 and 0.9841 with a SD of 0.0225, respectively