Fig. 2

Quantification of cfDNA concentration in blood plasma. (A) Comparison of cfDNA concentrations determined by fluorometric analysis and short single-locus qPCR. Linear regression is shown for all data (black line, n = 486) and for data with detectable cfDNA using fluorometric analysis (grey line, n = 343). Pearson correlation coefficients (r) were calculated. Dashed line corresponds to lowest quantified cfDNA concentration divided by two. Samples with no fluorometric readout due to too low cfDNA concentrations are shown in red (n = 143). Three samples marked with arrows were considered technical outliers. (B) Concentration of cfDNA quantified using single-locus versus multi-locus qPCR assays. Linear regression is shown (n = 486). Pearson correlation coefficient was calculated. Dashed line corresponds to lowest quantified cfDNA concentration divided by two. One sample marked in red was considered a technical outlier using short multi-locus qPCR. (C) Concentration of cfDNA collected in K₂EDTA, Norgen, PAXgene and Streck tubes with plasma isolation after 0, 48 and 168 h. Plasma from K₂EDTA, PAXgene and Streck tubes was centrifugated twice, while plasma from Norgen tubes was centrifugated once, according to manufacturers’ instructions. The mean cfDNA concentration is indicated by a bar and below the data points. Wilcoxon signed-ranked test was used, * p ≤ 0.05, ** p ≤ 0.01, *** p ≤ 0.001, **** p ≤ 0.0001 and ns, not significant. (D) Concentration of cfDNA collected in K₂EDTA, Norgen, PAXgene and Streck tubes with plasma isolation at 0 h. Data were rearranged from subfigure C for visualization purposes. Wilcoxon signed-ranked test was used, **** p ≤ 0.0001 and ns, not significant.