PF4 and chronic kidney disease: After normalization to kidney function, the plasma PF4/Cr ratios were 298.8 (168.2–616.6), 155.7 (75.4–281), 89.7 (62.5–150.3), and 21.2 (4.6–37.8) μg/mg Cr in children with CKD stages G1, G2, G3, and G4, respectively.