Hepcidin-25: Measurement by LC-MS/MS in serum and urine, reference ranges and urinary fractional excretion

A liquid chromatography tandem-mass spectrometry (LC-MS/MS) method was developed for reliably quantifying hepcidin-25 in human urine and serum. A 95% reference range was established for serum hepcidin-25 levels by standardizing the sampling time between 8:00am and 11:00am in 90 apparently healthy volunteers. The association between hepcidin-25 concentration and other biological parameters was studied using multivariable analysis and the coefficient of renal excretion of hepcidin-25 was calculated. Preanalytical variables were also investigated. The LC-MS/MS method was validated using a recent validation strategy based on accuracy profiles. Good results were obtained in terms of trueness, precision, and linearity in the following dosing ranges: from 0.77 to 200nmol/L for urine and from 0.48 to 100nmol/L for serum. The 95% reference range of serum hepcidin-25 concentration established after excluding known conditions that affect hepcidin-25 expression was 1.5 to 15.2nmol/L. A difference between genders was demonstrated with a median concentration of 5.5 versus 7.2nmol/L for women and men, respectively. Serum hepcidin-25 concentrations were strongly correlated with ferritin and, to a lesser extent, with iron levels. The coefficient of renal excretion ranged from 0.1 to 16.4%. Higher values of hepcidin-25 concentrations were observed on ethylene diamine tetraacetate tubes compared to serum or lithium-heparin devices.