Objective: To explore the clinical application of plasma cell-free double-stranded DNA (cf-dsDNA) in the diagnosis of primary hepatic carcinomas (PHC). Methods: Sixty-two PHC patients and 41 patients with benign liver disease and 45 healthy controls were recruited. All subjects were required to fill in a questionnaire, and the fasting blood samples were taken from healthy individuals and pre-treatment patients. The plasma cf-dsDNA was extracted by magnetic bead method and the concentration was determined by Qubit 3.0 fluorometer. The serum tumor markers AFP, CA19-9, CA12-5 and CEA levels were measured by electrochemiluminescence. The differences in plasma cf-dsDNA levels in each group of patients and the relationship between plasma cf-dsDNA levels and the clinical characteristics of PHC patients were analyzed, and receiver operating characteristic (ROC) curves were used to analyze the diagnostic efficiency of cf-dsDNA for PHC. Results: The median of preoperative cf-dsDNA levels in PHC patients was significantly higher than those in patients with benign liver disease or healthy controls (H=93.54, P<0.01). In PHC patients, there was no difference in cf-dsDNA levels between age, gender, AFP level, PHC type, and tumor size (all of P>0.05). There was a certain rank correlation between cf-dsDNA levels and TNM stage of PHC patients (r_s=0.311, P=0.013 9). Compared with other tumor markers, cf-dsDNA had higher diagnostic efficiency for PHC (AUC=0.965). According to the cut-off value (>1.912 ng/μL), the positive rate of cf-dsDNA in PHC was 90.32% (56/62), which was significantly higher than other tumor markers (x²= 36.00, P<0.01). Conclusion: Plasma cf-dsDNA was a promising non-invasive marker for PHC diagnosis.

［Key words］cell-free double-stranded DNA； tumor marker； primary hepatic carcinomas； diagnosis