MicroRNA hemolysis marker correlates with platelet contamination in low-hemolysis plasma samples. (A) Differences in plasma miRNAs miR-23a and miR-451 indicate low hemolysis (Δ < 5). There were no statistically significant differences in the level of hemolysis between sham (n = 3) and TBI rats (n = 4) at any of the measured time points (baseline, 2 d, 7 d, and 3 months post-TBI); data from the different time points were pooled after analysis as shown in panel A. (B) Pearson’s correlation indicated that the higher the ratio of miR-451a to miR-23a, the higher the miR-425 content in tested samples (r = - 0.541, **p < 0.01). A lower cycle value (Cq, y-axis) in the PCR analysis represents a higher expression level. Abbreviations: Cq, quantification cycle, r = Pearson correlation coefficient; TBI, traumatic brain injury. Whiskers in panel A represent min and max values.