The observed differences in absolute concentrations may be due to the inability of the c-ELISA to distinguish between the hepcidin isoforms, because it cross-reacts 47% and 68% with the respective hepcidin-22 and -20 isoforms in a given sample.
3, the relative differences between median hepcidin concentrations observed for all diseases were similar for the WCX-TOF-MS and the c-ELISA.
4 times lower than the mean c-ELISA (total) hepcidin concentrations.
In contrast, ferritin correlated significantly with hepcidin concentrations measured by c-ELISA and ICTOF-MS (R = 0.
Absolute hepcidin concentrations differed between c-ELISA and the WCX-TOF-MS, corroborating previous findings (17).
The presence of hepcidin isoforms has been reported previously for patients with CKD and hemodialysis (6, 18) and these insoforms likely contributed to the here described differences in reported WCX-TOF-MS (hepcidin-25) and c-ELISA (total) hepcidin concentrations.
Comparison of c-ELISA and IC-TOF-MS methodology, which is also referred to as mass-spectrometric immunoassay, is not novel but has provided valuable insights as to the isoform specificity of assays (27).
We found both the c-ELISA and the IC-TOF-MS to better differentiate anemic RA patients with IDA from those with IDA and ACD than WCX-TOF-MS.
We found our c-ELISA to be more sensitive and less specific for hepcidin-25 compared to our WCX-TOF-MS assay.
We conclude that c-ELISA is the current method of first choice for the quantification of serum hepcidin, because of its low limit of detection, low costs, and high throughput.
6] Nonstandard abbreviations: MS, mass spectrometry; c-ELISA competitive ELISA, IC, immunocapture; WCX, weak cation exchange; IDA, iron deficiency anemia; ACD, anemia of chronic diseases; MM, multiple myeloma; HH, hereditary hemochromatosis; CKD, chronic kidney disease; RA, rheumatoid arthritis; LLOD, lower limit of detection; pI, isoelectric point.
WCX-TOF-MS c-ELISA Analytical LLOD, pmol/L NA (a) 20.