Biological variability of cell-free DNA in healthy females at rest within a short time course

Introduction: Alterations in cell-free DNA concentration (cfDNA) over time have been studied in diseased or injured patients or analyzed in athletes during exhaustive exercise. However, no fluctuations have been examined over a short time course in healthy humans at rest so far, wherefore the aim of this study was to examine individual variations at different time points within 75 min. Methods: Serial blood drawing was performed in 14 healthy female volunteers at rest within 75 min. Plasma DNA was quantified by real-time qPCR, and absolute levels were analyzed together with relative variations. cfDNA alterations were moreover analyzed in consideration of potential volunteer-related impact factors (e.g., pulse) and were compared to alterations of plasma CK and AST. Results: Absolute cfDNA concentration ranged from 0.6 to 3.4 ng/ml. Regarding alterations over time, positive and negative variations were identified, whereby the interdecile range of fold changes was from 0.5 to 1.4. The maximum fold change was determined at 10 min. No relations were found between cfDNA levels and the analyzed individual factors. Conclusion: We evidenced the variability of cfDNA in healthy humans at rest within a short time course. The determined variations should serve in future studies to distinguish small cfDNA increases after minor trauma from natural fluctuations. Without such reference of intra-individual variation at rest, it would not be feasible to distinguish an injury from a fluctuation with certainty. Thus, a basis was established for the application of cfDNA as biomarker for the detection of mild injuries in forensic biomechanics.