Evaluation of a method for fibroblast growth factor-23: a novel biomarker of adverse outcomes in patients with renal disease
Background: Fibroblast growth factor 23 (FGF-23), a phosphaturic peptide hormone
secreted by the osteoblasts, is an important regulator of phosphorus and vitamin D
metabolism. In chronic kidney disease, FGF-23 levels rise with declining kidney function.
Increasing FGF-23 levels are associated with increasing risk of mortality in dialysis patients.
Two assays for FGF-23 have been reported. One assay detects only full-length/intact FGF-
23. In contrast, the carboxy-terminal assay recognizes both intact and carboxy-terminal FGF …
secreted by the osteoblasts, is an important regulator of phosphorus and vitamin D
metabolism. In chronic kidney disease, FGF-23 levels rise with declining kidney function.
Increasing FGF-23 levels are associated with increasing risk of mortality in dialysis patients.
Two assays for FGF-23 have been reported. One assay detects only full-length/intact FGF-
23. In contrast, the carboxy-terminal assay recognizes both intact and carboxy-terminal FGF …
Abstract
Background: Fibroblast growth factor 23 (FGF-23), a phosphaturic peptide hormone secreted by the osteoblasts, is an important regulator of phosphorus and vitamin D metabolism. In chronic kidney disease, FGF-23 levels rise with declining kidney function. Increasing FGF-23 levels are associated with increasing risk of mortality in dialysis patients. Two assays for FGF-23 have been reported. One assay detects only full-length/intact FGF-23. In contrast, the carboxy-terminal assay recognizes both intact and carboxy-terminal FGF-23.
Aim/Methods: The aim of this study was to evaluate both assays for FGF-23. Test samples were analyzed with both the intact and carboxy-terminal FGF-23 enzyme-linked immunosorbent assay (ELISA) kits according to manufacturers' instructions.
Results: Carboxy-terminal FGF-23 showed very good precision with coefficients of variation (CV) ranging from 4% to 10.5%, whereas the CVs for intact FGF-23 were not very good (6–37.5%). The carboxy-terminal assay was linear, stable in plasma samples, and was not affected by common interferents. Also, the carboxy-terminal FGF-23 assay appeared to correlate better with worsening of kidney function as assessed by plasma creatinine and calculated estimated glomerular filtration rate (eGFR).
Conclusion: Thus, the carboxy-terminal FGF-23 assay is robust and can be used in prospective trials to validate its utility as a biomarker of adverse outcomes in patients with renal disease.
Mary Ann Liebert