KLK1 and acute kidney injury: Promoter KLK1 methylation in blood DNA was also higher in AKI than controls (70.32 ± 2.27 vs. 65.36 ± 1.05%; ANOVA p = 0.011), while promoter KLK1 methylation in urine DNA trended to be higher in AKI than controls (40.95 ± 7.06 vs. 30.35 ± 5.88%; ANOVA p = 0.22; Figure 4).