BACKGROUND: Fibroblast growth factor 23 (FGF-23) is a recently discovered hormone, which plays a key role in phosphate regulation. To investigate whether FGF-23 can be determined reliably, we validated the three available FGF-23 assays. METHODS: Currently, two intact FGF-23 assays (Kainos; Immutopics) and one C-terminal FGF-23 assay (Immutopics) are available. We determined intra- and inter-assay variation, linearity and matrix interference in these assays. Moreover, we compared assay results from healthy subjects with those of patient groups with expected high FGF-23 concentrations. RESULTS: Intra-assay variation was reasonably good in all three assays. Inter-assay variation and linearity were poor for the intact Immutopics assay but reasonable for both other assays. Immutopics assays gave best results in ethylenediaminetetraacetic acid (EDTA) plasma, while the Kainos assay showed comparable reproducibility in EDTA plasma and serum. Although the manual of the Kainos assay states that an automatic washing machine can be used, acceptable results were only found by manual washing. Patients with kidney disease and patients with hypophosphatemic osteomalacia had increased C-terminal FGF-23 concentrations compared with healthy controls. CONCLUSION: Two assays of reasonable quality are available for FGF-23, the intact FGF-23 assay (Kainos) provided proper attention is paid to the washing procedure, and the C-terminal assay (Immutopics).
BACKGROUND:Fibroblast growth factor 23 (FGF-23) is a recently discovered hormone, which plays a key role in phosphate regulation. To investigate whether FGF-23 can be determined reliably, we validated the three available FGF-23 assays. METHODS: Currently, two intact FGF-23 assays (Kainos; Immutopics) and one C-terminal FGF-23 assay (Immutopics) are available. We determined intra- and inter-assay variation, linearity and matrix interference in these assays. Moreover, we compared assay results from healthy subjects with those of patient groups with expected high FGF-23 concentrations. RESULTS: Intra-assay variation was reasonably good in all three assays. Inter-assay variation and linearity were poor for the intact Immutopics assay but reasonable for both other assays. Immutopics assays gave best results in ethylenediaminetetraacetic acid (EDTA) plasma, while the Kainos assay showed comparable reproducibility in EDTA plasma and serum. Although the manual of the Kainos assay states that an automatic washing machine can be used, acceptable results were only found by manual washing. Patients with kidney disease and patients with hypophosphatemic osteomalacia had increased C-terminal FGF-23 concentrations compared with healthy controls. CONCLUSION: Two assays of reasonable quality are available for FGF-23, the intact FGF-23 assay (Kainos) provided proper attention is paid to the washing procedure, and the C-terminal assay (Immutopics).
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: Marc G Vervloet; Frans J van Ittersum; Rahel M Büttler; Annemieke C Heijboer; Marinus A Blankenstein; Piet M ter Wee Journal: Clin J Am Soc Nephrol Date: 2010-10-28 Impact factor: 8.237
Authors: Christopher T Sempos; Annemieke C Heijboer; Daniel D Bikle; Jens Bollerslev; Roger Bouillon; Patsy M Brannon; Hector F DeLuca; Glenville Jones; Craig F Munns; John P Bilezikian; Andrea Giustina; Neil Binkley Journal: Br J Clin Pharmacol Date: 2018-07-17 Impact factor: 4.335
Authors: Charlotte A Keyzer; Martin H de Borst; Else van den Berg; Willi Jahnen-Dechent; Spyridon Arampatzis; Stefan Farese; Ivo P Bergmann; Jürgen Floege; Gerjan Navis; Stephan J L Bakker; Harry van Goor; Ute Eisenberger; Andreas Pasch Journal: J Am Soc Nephrol Date: 2015-04-29 Impact factor: 10.121
Authors: Leandro C Baia; Jelmer K Humalda; Marc G Vervloet; Gerjan Navis; Stephan J L Bakker; Martin H de Borst Journal: Clin J Am Soc Nephrol Date: 2013-08-08 Impact factor: 8.237