A novel method for extracting circulating cell-free DNA from whole blood samples and its utility in the non-invasive prenatal test.

Objective: We verified a magnetic bead-based, simple, and fast method for circulating cell-free DNA (cfDNA) extraction from whole blood samples(CEWB) and characterised its utility in non-invasive prenatal testing (NIPT).

Method: We extracted cfDNA from both plasma and whole blood of the patients using CEWB and compared it to that extracted using a Qiagen extraction kit; droplet digital polymerase chain reaction test was used to calculate the fragment size bias. In all, 304 samples were used for NIPT.

Results: The CEWB group (mean ± standard deviation [SD]: 4.34 ± 0.41 ng/ml plasma) reported less DNA weight yield than the Qiagen group (4.90 ± 0.50 ng/ml plasma). There was no significant difference between the CEWB group and the Qiagen group in the gene fragments (136 bp: p = 0.064 and 420 bp: p = 0.534). In a parallel cohort study to characterise the utility of the CEWB method in NIPT, the treatment group extracted by CEWB showed a sensitivity of 100%, a specificity of 99.65%, and a positive predictive value of 95%.

Conclusions: This study demonstrated that CEWB achieves an acceptable yield of DNA without contamination from genomic DNA. Subsequent clinical experiments in a parallel cohort indicated its utility for NIPT.