Cell destruction results in plasma accumulation of cell-free DNA (cfDNA). Dynamic changes in circulating lymphocytes are features of COVID-19. We aimed to investigate if cfDNA level can serve in stratification of COVID-19 patients, and if cfDNA level is associated with alterations in lymphocyte subsets and neutrophil-to-lymphocyte ratio (NLR). This cross-sectional comparative study enrolled 64 SARS-CoV-2-positive patients. Patients were subdivided to severe and non-severe groups. Plasma cfDNA concentration was determined by real-time quantitative PCR. Lymphocyte subsets were assessed by flow cytometry. There was significant increase in cfDNA among severe cases when compared with non-severe cases. cfDNA showed positive correlation with NLR and inverse correlation with T cell percentage. cfDNA positively correlated with ferritin and C-reactive protein. The output data of performed ROC curves to differentiate severe from non-severe cases revealed that cfDNA at cut-off ≥17.31 ng/µl and AUC of 0.96 yielded (93%) sensitivity and (73%) specificity. In summary, excessive release of cfDNA can serve as sensitive COVID-19 severity predictor. There is an association between cfDNA up-regulation and NLR up-regulation and T cell percentage down-regulation. cfDNA level can be used in stratification and personalized monitoring strategies in COVID-19 patients.

细胞破坏导致血浆中无细胞DNA（cfDNA）的积累。循环淋巴细胞的动态变化是COVID-19的特征。我们旨在研究cfDNA水平是否可用于COVID-19患者的分层，以及cfDNA水平是否与淋巴细胞亚群和中性粒细胞与淋巴细胞比率（NLR）的改变有关。这项横断面的比较研究招募了64名SARS-CoV-2阳性患者。患者分为重度和非重度组。通过实时定量PCR确定血浆cfDNA浓度。通过流式细胞术评估淋巴细胞亚群。与非严重病例相比，严重病例的cfDNA显着增加。cfDNA与NLR呈正相关，与T细胞百分比呈负相关。cfDNA与铁蛋白和C反应蛋白呈正相关。所执行的ROC曲线的输出数据可区分严重病例与非严重病例，结果表明cfDNA的截止值≥17.31ng / µl，AUC为0.96，灵敏度（93％）和特异性（73％）。总之，cfDNA的过度释放可作为敏感的COVID-19严重程度预测指标。cfDNA上调与NLR上调与T细胞百分比下调之间存在关联。cfDNA水平可用于COVID-19患者的分层和个性化监测策略。cfDNA上调与NLR上调与T细胞百分比下调之间存在关联。cfDNA水平可用于COVID-19患者的分层和个性化监测策略。cfDNA上调与NLR上调与T细胞百分比下调之间存在关联。cfDNA水平可用于COVID-19患者的分层和个性化监测策略。