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Instability of fibroblast growth factor-23 (FGF-23): implications for clinical studies
journal contributionposted on 2023-06-08, 14:50 authored by Edward R Smith, Martin L Ford, Laurie A Tomlinson, Gary Weaving, Bernard F Rocks, Chakravarthi RajkumarChakravarthi Rajkumar, Stephen G Holt
BACKGROUND Fibroblast growth factor-23 (FGF-23) is a bone secreted hormone that regulates phosphate homeostasis and calcitriol levels. FGF-23 concentrations are elevated in chronic kidney disease (CKD), oncogenic osteomalcia and a number of rare hereditary disorders. Studies systematically evaluating the pre-analytical stability of intact FGF-23 are lacking. METHODS The stability of FGF-23 was assessed in timed experiments using blood taken into K2-EDTA plasma specimen tubes from a group of healthy participants and from a group with mild-to-moderate CKD. We evaluated the use of aprotinin, a serine protease inhibitor, and a commercially available protease inhibitor cocktail to preserve intact FGF-23 after blood collection. FGF-23 measurements were made using both intact and C-terminal assays. RESULTS Both whole blood and separated sample studies demonstrated a rapid loss of intact FGF-23 within 2 h, while concentrations increased using the C-terminal assay. The addition of protease inhibitor cocktail stabilised FGF-23 concentrations for 4 h after blood collection. Intact and C-terminal assay FGF-23 measurements showed poor correlation in both healthy and CKD cohorts. CONCLUSION K2-EDTA plasma samples, even when promptly separated, are unsuitable for measurement of FGF-23 unless stabilised with a protease inhibitor cocktail.
JournalClinica Chimica Acta
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- Clinical and Experimental Medicine Publications
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