Deviations from the Expected Relationship Between Serum FGF23 and Other Markers in Children with CKD: a cross-sectional study.

BACKGROUND: High levels of fibroblast growth factor-23 (FGF23) are associated with mortality. In chronic kidney disease (CKD), FGF23 levels rise as renal function declines. We analyzed the contribution of laboratory values to the variance of FGF23 levels in relationship to a curve of expected FGF23 levels for a given GFR. METHODS: Following approval by the research ethics boards, we measured FGF23, CysC eGFR, creatinine, urea, albumin, calcium, phosphate, vitamin D metabolites, PTH, alkaline phosphatase, CRP, and venous gases in 141 pediatric CKD patients (45, 37, 32, 13 and 14 CKD stages I, II, III, IV, and V, respectively). Data were expressed as median (25th, 75th percentile). RESULTS: FGF23 correlated significantly with CysC, CysC eGFR, PTH, 1.25 (OH) CONCLUSIONS: Our data emphasize the importance of phosphate and 1.25 (OH