BACKGROUND: The measurement of the serum concentration of fibroblast growth factor-23 (FGF-23) is beginning to be used as a diagnostic tool in renal phosphate wasting disorders. Having observed an increased serum FGF-23 in three subjects with low circulating ferritin concentrations we investigated the association between low ferritin and raised serum FGF-23. METHODS: We measured FGF-23 in 150 random anonymized serum samples with ferritin concentrations between <5 and 50 microg/L using three commercially available enzyme-linked immunosorbent assay (ELISA) kits. One kit, Human FGF-23[C-term] (Immutopics Inc, USA) measures total FGF-23 whereas the other two kits, Immutopics intact and FGF-23 ELISA (Kainos, Japan) are reported to measure only the biologically active intact molecule. RESULTS: We have detected a significant inverse correlation of -0.565 (P<0.0001) between serum ferritin when <50 microg/L and FGF-23 using the C-terminal assay. This relationship is also shown with the Immutopics intact assay but is not demonstrated with the Kainos intact assay. CONCLUSION: The measurement of FGF-23 by both Immutopics assays is altered in the presence of low circulating concentrations of serum ferritin whereas with the Kainos intact assay this effect was not demonstrated. Serum ferritin should be measured when an elevated FGF-23 is obtained using the Immutopics C-terminal or intact FGF-23 assay to prevent misdiagnosis of the cause of this abnormality.
BACKGROUND: The measurement of the serum concentration of fibroblast growth factor-23 (FGF-23) is beginning to be used as a diagnostic tool in renal phosphate wasting disorders. Having observed an increased serum FGF-23 in three subjects with low circulating ferritin concentrations we investigated the association between low ferritin and raised serum FGF-23. METHODS: We measured FGF-23 in 150 random anonymized serum samples with ferritin concentrations between <5 and 50 microg/L using three commercially available enzyme-linked immunosorbent assay (ELISA) kits. One kit, HumanFGF-23[C-term] (Immutopics Inc, USA) measures total FGF-23 whereas the other two kits, Immutopics intact and FGF-23 ELISA (Kainos, Japan) are reported to measure only the biologically active intact molecule. RESULTS: We have detected a significant inverse correlation of -0.565 (P<0.0001) between serum ferritin when <50 microg/L and FGF-23 using the C-terminal assay. This relationship is also shown with the Immutopics intact assay but is not demonstrated with the Kainos intact assay. CONCLUSION: The measurement of FGF-23 by both Immutopics assays is altered in the presence of low circulating concentrations of serum ferritin whereas with the Kainos intact assay this effect was not demonstrated. Serum ferritin should be measured when an elevated FGF-23 is obtained using the Immutopics C-terminal or intact FGF-23 assay to prevent misdiagnosis of the cause of this abnormality.
Authors: Michele F Eisenga; Marco van Londen; David E Leaf; Ilja M Nolte; Gerjan Navis; Stephan J L Bakker; Martin H de Borst; Carlo A J M Gaillard Journal: J Am Soc Nephrol Date: 2017-08-03 Impact factor: 10.121
Authors: Emily G Farrow; Xijie Yu; Lelia J Summers; Siobhan I Davis; James C Fleet; Matthew R Allen; Alexander G Robling; Keith R Stayrook; Victoria Jideonwo; Martin J Magers; Holly J Garringer; Ruben Vidal; Rebecca J Chan; Charles B Goodwin; Siu L Hui; Munro Peacock; Kenneth E White Journal: Proc Natl Acad Sci U S A Date: 2011-10-17 Impact factor: 11.205
Authors: Erik A Imel; Munro Peacock; Amie K Gray; Leah R Padgett; Siu L Hui; Michael J Econs Journal: J Clin Endocrinol Metab Date: 2011-08-31 Impact factor: 5.958
Authors: Mark R Hanudel; Kristine Chua; Maxime Rappaport; Victoria Gabayan; Erika Valore; David Goltzman; Tomas Ganz; Elizabeta Nemeth; Isidro B Salusky Journal: Am J Physiol Renal Physiol Date: 2016-10-12
Authors: Katherine Wesseling-Perry; Renata C Pereira; Hejing Wang; Robert M Elashoff; Shobha Sahney; Barbara Gales; Harald Jüppner; Isidro B Salusky Journal: J Clin Endocrinol Metab Date: 2008-12-02 Impact factor: 5.958