Univariate analysis showed that there is not a significant correlation between serum FGF23 and renal α-KL levels in CKD patients at stage 1 (r = −0.123, P = 0.3482), 2 (r = −0.033, P = 0.7687) or 3 (r = −0.251, P = 0.0696), but there is a significant inverse correlation at stages 4–5 (r = −0.686, P<0.0001) (Figure 5A–D). Here, FGF23 is linked to chronic kidney disease.