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Cell-free DNA (cfDNA) analysis is a pivotal tool in non-invasive diagnostics, including cancer monitoring and prenatal testing. However, the preanalytical phase, particularly the choice of anticoagulant, significantly impacts cfDNA integrity and yield. This study aims to compare cfDNA yield, stability, and DNase activity across plasma-citrate, plasma-heparin, plasma-EDTA, and serum, to identify the most suitable specimen for cfDNA analysis among the tested anticoagulants. Blood samples from 15 healthy volunteers were collected in four types of tubes (citrate, heparin, EDTA, and serum). cfDNA was extracted and quantified using qPCR, and endogenous DNase activity was assessed through hydrolysis probe assays. Samples were incubated at 37°C for 24 hours to evaluate cfDNA degradation rates. Statistical analyses were performed using repeated measures ANOVA and Sidak's multiple comparison tests. Baseline cfDNA levels were highest in serum, followed by heparin-plasma, while EDTA and citrate-plasma exhibited the lowest levels. DNase activity was fully inhibited in EDTA-plasma, partially inhibited in citrate-plasma, and active in both heparin-plasma and serum. cfDNA degradation was most pronounced in heparin-plasma (85.3%) and serum (55.6%), compared to minimal degradation in EDTA (8%) and citrate-plasma (13.3%). Among the tested anticoagulants, EDTA-plasma proved to be the most suitable specimen for cfDNA analysis due to its low DNase activity and minimal gDNA contamination. Citrate-plasma, with intermediate DNase inhibition, could be an alternative if the citrate concentration were increased. Heparin-plasma and serum showed significant cfDNA degradation, rendering them unsuitable for cfDNA analysis. These findings highlight the importance of anticoagulant selection in preserving cfDNA integrity for diagnostic applications.