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Evaluation of a New Fully Automated Assay for Plasma Intact FGF23.

Jean-Claude SouberbielleDominique PriéMarie-Liesse PikettyAnya RothenbuhlerPierre DelanayePhilippe ChansonCavalier Etienne
Published in: Calcified tissue international (2017)
Several FGF23 immunoassays are available. However, they are reserved for research purposes as none have been approved for clinical use. We evaluated the performances of a new automated assay for intact FGF23 on the DiaSorin Liaison platform which is approved for clinical use. We established reference values in 908 healthy French subjects aged 18-89 years, and measured iFGF23 in patients with disorders of phosphate metabolism and in patients with chronic kidney disease (CKD). Intra-assay CV was 1.04-2.86% and inter-assay CV was 4.01-6.3%. The limit of quantification was <10 ng/L. Serum iFGF23 concentrations were considerably lower than EDTA values highlighting the importance of using exclusively EDTA plasma. Liaison iFGF23 values were approximately 25% higher than Immutopics values. In the 908 healthy subjects, distribution of the Liaison iFGF23 values was Gaussian with a mean ± 2SD interval of 22.7-93.1 ng/L. Men had a slightly higher level than women (60.3 ± 17.6 and 55.2 ± 17.2 ng/L, respectively). Plasma iFGF23 concentration in 11 patients with tumour-induced osteomalacia, 8 patients with X-linked hypophosphatemic rickets, 43 stage 3a, 43 stage 3b, 43 stage 4, 44 stage 5 CKD patients, and 44 dialysis patients were 217.2 ± 144.0, 150.9 ± 28.6, 98.5 ± 42.0, 130.8 ± 88.6, 130.8 ± 88.6, 331.7 ± 468.2, 788.8 ± 1306.6 and 6103.9 ± 11,178.8 ng/L, respectively. This new iFGF23 assay available on a platform that already allows the measurement of other important parameters of the mineral metabolism is a real improvement for the laboratories and clinicians/researchers involved in this field.
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