Abstract
Background: There is growing interest in measuring plasma fibroblast growth factor 23 (FGF23) concentration in a number of clinical settings. However, data comparing current commercial intact and C-terminal FGF23 assays is lacking.
Methods: We used plasma samples collected from a cohort of healthy adults and patients undergoing chronic haemodialysis therapy (n=67) to compare the precision, recovery, linearity and pre-analytical stability characteristics of four commercial FGF23 assays from Kainos, Millipore and Immutopics Inc. Method agreement was evaluated using Passing-Bablok regression and difference plot analysis.
Results: Both Millipore and Immutopics intact FGF23 kits demonstrated marked negative proportional bias relative to Kainos assay readout, particularly in the haemodialysis group, and poor recovery of purified FGF23 standard at high spiking concentrations. Dilution of high-reading samples with saline as recommended by the Immutopics kit resulted in significant deviation from linearity. Immutopics C-terminal FGF23 concentrations displayed a strong association with intact FGF23 concentrations determined with all three intact assays in the haemodialysis group, but showed no significant correlation within the physiological range. Only intact FGF23 measurements made with the Immutopics assay demonstrated evidence of significant instability 8 h after venepuncture.
Conclusions: Current ELISA kits for plasma intact FGF23 measurement show poor analytical agreement, and cannot be used interchangeably. This is mainly due to differences in calibration. Harmonisation of available assays using a common international standard would facilitate more meaningful interpretation of data from studies using different kits. Discordance between intact and C-terminal FGF23 assay measurements is more marked at physiological concentrations than in patients undergoing haemodialysis.
We thank Dr. Michael MX Cai (Eastern Health, Box Hill) for assisting with patient recruitment and procurement of samples for this study.
Conflict of interest statement
Authors’ conflict of interest disclosure: The authors stated that there are no conflicts of interest regarding the publication of this article. Research funding played no role in the study design; in the collection, analysis, and interpretation of data; in the writing of the report; or in the decision to submit the report for publication.
Research funding: This work was partly funded by an unrestricted investigator-initiated research grant from Amgen Australia Pty Ltd and financial assistance from Eastern Health and Monash University.
Employment or leadership: None declared.
Honorarium: ERS has received honoraria from Shire; SGH has received honoraria from Amgen, Baxter and Shire.
References
1. Shimada T, Hasegawa H, Yamazaki Y, Muto T, Hino R, Takeuchi Y, et al. FGF-23 is a potent regulator of vitamin D metabolism and phosphate homeostasis. J Bone Miner Res 2004;19:429–35.10.1359/JBMR.0301264Search in Google Scholar PubMed
2. Shimada T, Kakitani M, Yamazaki Y, Hasegawa H, Takeuchi Y, Fujita T, et al. Targeted ablation of Fgf23 demonstrates an essential physiological role of FGF23 in phosphate and vitamin D metabolism. J Clin Invest 2004;113:561–8.10.1172/JCI200419081Search in Google Scholar
3. Wolf M. Forging forward with 10 burning questions on FGF23 in kidney disease. J Am Soc Nephrol 2010;21:1427–35.10.1681/ASN.2009121293http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=000283345000009&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=b7bc2757938ac7a7a821505f8243d9f3Search in Google Scholar PubMed
4. Isakova T, Xie H, Yang W, Xie D, Anderson AH, Scialla J, et al. Fibroblast growth factor 23 and risks of mortality and end-stage renal disease in patients with chronic kidney disease. J Am Med Assoc 2011;305:2432–9.10.1001/jama.2011.826Search in Google Scholar PubMed PubMed Central
5. Fliser D, Kollerits B, Neyer U, Ankerst DP, Lhotta K, Lingenhel A, et al. Fibroblast growth factor 23 (FGF23) predicts progression of chronic kidney disease: the Mild to Moderate Kidney Disease (MMKD) Study. J Am Soc Nephrol 2007;18: 2600–8.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=000250986000024&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=b7bc2757938ac7a7a821505f8243d9f310.1681/ASN.2006080936Search in Google Scholar PubMed
6. Gutierrez OM, Januzzi JL, Isakova T, Laliberte K, Smith K, Collerone G, et al. Fibroblast growth factor 23 and left ventricular hypertrophy in chronic kidney disease. Circulation 2009;119:2545–52.10.1161/CIRCULATIONAHA.108.844506Search in Google Scholar PubMed PubMed Central
7. Gutierrez OM, Mannstadt M, Isakova T, Rauh-Hain JA, Tamez H, Shah A, et al. Fibroblast growth factor 23 and mortality among patients undergoing hemodialysis. N Engl J Med 2008;359: 584–92.10.1056/NEJMoa0706130http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=000258216700006&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=b7bc2757938ac7a7a821505f8243d9f3Search in Google Scholar PubMed PubMed Central
8. Oliveira RB, Cancela AL, Graciolli FG, Dos Reis LM, Draibe SA, Cuppari L, et al. Early control of PTH and FGF23 in normophosphatemic CKD patients: a new target in CKD-MBD therapy? Clin J Am Soc Nephrol 2010;5:286–91.10.2215/CJN.05420709Search in Google Scholar PubMed PubMed Central
9. Yamashita T. Structural and biochemical properties of fibroblast growth factor 23. Ther Apher Dial 2005;9:313–8.10.1111/j.1744-9987.2005.00288.xSearch in Google Scholar PubMed
10. Benet-Pages A, Lorenz-Depiereux B, Zischka H, White KE, Econs MJ, Strom TM. FGF23 is processed by proprotein convertases but not by PHEX. Bone 2004;35: 455–62.10.1016/j.bone.2004.04.002Search in Google Scholar PubMed
11. Smith ER, Cai MM, McMahon LP, Holt SG. Biological variability of plasma intact and C-terminal FGF23 measurements. J Clin Endocrinol Metab 2012;97:3357–65.10.1210/jc.2012-1811http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=000308692900077&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=b7bc2757938ac7a7a821505f8243d9f3Search in Google Scholar PubMed
12. Ito N, Fukumoto S, Takeuchi Y, Yasuda T, Hasegawa Y, Takemoto F, et al. Comparison of two assays for fibroblast growth factor (FGF)-23. J Bone Miner Metab 2005;23: 435–40.10.1007/s00774-005-0625-4Search in Google Scholar PubMed
13. Wesseling-Perry K. FGF23: is it ready for prime time? Clin Chem 2011;57:1476–7.10.1373/clinchem.2011.172890Search in Google Scholar PubMed
14. Smith ER, Cai MM, McMahon LP, Pedagogos E, Toussaint ND, Brumby C, et al. Serum fetuin-A concentration and fetuin-A-containing calciprotein particles in patients with chronic inflammatory disease and renal failure. Nephrology (Carlton) 2013;18:215–21.10.1111/nep.12021http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=000315405600011&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=b7bc2757938ac7a7a821505f8243d9f3Search in Google Scholar PubMed
15. Smith ER, Ford ML, Tomlinson LA, Weaving G, Rocks BF, Rajkumar C, et al. Instability of fibroblast growth factor-23 (FGF-23): implications for clinical studies. Clin Chim Acta 2011;412:1008–11.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=000291125200035&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=b7bc2757938ac7a7a821505f8243d9f310.1016/j.cca.2011.02.009Search in Google Scholar PubMed
16. Yamazaki Y, Okazaki R, Shibata M, Hasegawa Y, Satoh K, Tajima T, et al. Increased circulatory level of biologically active full-length FGF-23 in patients with hypophosphatemic rickets/osteomalacia. J Clin Endocrinol Metab 2002;87: 4957–60.10.1210/jc.2002-021105Search in Google Scholar PubMed
17. Shimada T, Urakawa I, Isakova T, Yamazaki Y, Epstein M, Wesseling-Perry K, et al. Circulating fibroblast growth factor 23 in patients with end-stage renal disease treated by peritoneal dialysis is intact and biologically active. J Clin Endocrinol Metab 2010;95:578–85.10.1210/jc.2009-1603http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=000274298200017&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=b7bc2757938ac7a7a821505f8243d9f3Search in Google Scholar PubMed PubMed Central
18. Yamamoto T, Nascimento MM, Hayashi SY, Qureshi AR, Waniewski J, Brodin LA, et al. Changes in circulating biomarkers during a single hemodialysis session. Hemodial Int 2012;17: 59–66.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=000313751100008&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=b7bc2757938ac7a7a821505f8243d9f3Search in Google Scholar PubMed
19. Imel EA, Peacock M, Pitukcheewanont P, Heller HJ, Ward LM, Shulman D, et al. Sensitivity of fibroblast growth factor 23 measurements in tumor-induced osteomalacia. J Clin Endocrinol Metab 2006;91:2055–61.10.1210/jc.2005-2105Search in Google Scholar PubMed
20. Heijboer AC, Levitus M, Vervloet MG, Lips P, ter Wee PM, Dijstelbloem HM, et al. Determination of fibroblast growth factor 23. Ann Clin Biochem 2009;46: 338–40.10.1258/acb.2009.009066Search in Google Scholar PubMed
21. Shimizu Y, Fukumoto S, Fujita T. Evaluation of a new automated chemiluminescence immunoassay for FGF23. J Bone Miner Metab 2012;30:217–21.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=000304824700011&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=b7bc2757938ac7a7a821505f8243d9f310.1007/s00774-011-0306-4Search in Google Scholar PubMed
22. Faul C, Amaral AP, Oskouei B, Hu MC, Sloan A, Isakova T, et al. FGF23 induces left ventricular hypertrophy. J Clin Invest 2011;121:4393–408.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=000296482700022&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=b7bc2757938ac7a7a821505f8243d9f310.1172/JCI46122Search in Google Scholar PubMed PubMed Central
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