Second round robin for plasma hepcidin methods: First steps toward harmonization

Joyce J.C. Kroot, Antonius E. van Herwaarden, Harold Tjalsma, Rob T.P. Jansen, Jan C.M. Hendriks, Dorine W. Swinkels

Measurements of the iron regulatory hormone hepcidin by various methodologies and laboratories are not harmonized. As a result different numeric results are obtained for the same clinical sample. We investigated whether better agreement between plasma hepcidin methods can be achieved by harmonization. Native plasma pools (n = 11) of a variety of hepcidin concentrations and blank plasma spiked with three different quantities of synthetic hepcidin-25 purchased from two different commercial sources (n = 6), were distributed in duplicate among 21 methods worldwide. We assessed commutability by comparing results from synthetic hepcidin with those from native samples in various method couples by Bland-Altman plots. Methods differed substantially in absolute values and reproducibility. For the majority of methods we found that samples with synthetic hepcidin-25 were noncommutable with the native samples. In an attempt to harmonize by using native hepcidin results, we selected two methods that showed good mutual agreement of native results and calculated consensus values as the medians for the 11 duplicate native samples obtained by these two methods. Finally, we constructed algorithms enabling the laboratories to calculate the hepcidin consensus (HEPCON) value using their own native hepcidin results. We found that the use of these algorithms substantially reduced the between-method CV. Until commutable materials are defined, hepcidin harmonization can be achieved by exploiting specific algorithms, allowing each lab to report their native hepcidin concentrations in HEPCON values. This study represents the first step toward harmonization of plasma hepcidin methods and facilitates aggregation of hepcidin data from different research investigations.