Abstract: Objective To establish a ALU-based branched DNA (bDNA) method for detection of human plasma circulating free DNA (cf-DNA) and investigate its concentration in acute myocardial infarction (AMI). Methods Based on the sequence of ALU, a bDNA method was established, Liner, sensitivity and reproducibility were evaluated; according to the standard curve created, the concentration of ALU in AMI were determined and the relationship of cf-DNA concentrations with cardiac enzymes were presented. Results The linear rang was 0-400 ng/mL, the coefficient correlation was 0.99，the intra-assay coefficient variation was 7.85%-11.75%, the inter-assay coefficient variation was10.05%-14.32%. The concentration of ALU in AMI and healthy controls were 4223 ng/mL and 118 ng/mL (P＜0.001) respectively indicating that ALU concentration was increased in AMI. No correlation was found among ALU and cardiac enzymes. The area under ROC was 0.99, the sensitivity was 98.8% and the specificity was 100.0%. Conclusions The ALU-based bDNA method is sensitive and reproductive; cf-DNA concentration is associated with AMI.

Key words: ALU, branched DNA, acute myocardial infarction