(A) The cfDNA copy number in normal subject (Plaque [-]) and subjects with carotid plaques. *P<0.05, **P<0.01 compared with Plaque (-). Closed circles represent current smokers. (B) Comparison of mt-cfDNA and n-cfDNA among four groups. *P<0.05, **P<0.01 compared with Plaque (-). (C) Correlation of cfDNA copy number with plaque thickness. (D) ROC analysis for atherosclerosis incidence (plaque [-] vs. plaque[+]), using mt-cfDNA and n-cfDNA. Abbreviations: AUC, area under the curve; mt-cfDNA, mitochondrial cell-free DNA; n-cfDNA, nuclear cell-free DNA.