FGF23 and chronic kidney disease: Moreover, multiple regression analysis of sKL using age, eGFR, renal α-KL, FGF23, intact PTH, 1,25VitD3, calcium and Pi levels as explanatory factors showed that serum sKL levels significantly correlate with renal α-KL (β = 0.803, P<0.001) as an independent contributing factor (R2 = 0.382, P<0.0001) across all CKD patients (Table 5).