Twelve biomarkers were measured in the blood of derivation cohort patients. Of these markers, eight were measured in the clinical laboratories of Chiba University Hospital within 4 hours of collection as routine laboratory measurements. Specifically, these were hemoglobin (Sysmex, Kobe, Japan), albumin, creatinine, Fe, TIBC, ferritin (Denka Seiken Co. Ltd., Tokyo, Japan), IL-6 (Roche Diagnostics, Mannheim, Germany), and transferrin saturation, which is calculated using the Fe and TIBC values. Erythropoietin, folate, vitamin B12 (Beckman Coulter, Tokyo, Japan), and transferrin (Nittobo Medical Co. Ltd., Tokyo, Japan) were measured in an external clinical laboratory (SRL. Inc., Tokyo, Japan). Albumin was measured as nutritional status.
The TIBC appeared to be a significant factor in the derivation cohort. It is known that IL-6 enhances synthesis of hepcidin and that increased hepcidin decreases serum levels of TIBC. Thus, to test for a biological plausibility, we additionally collected plasma and added measurements of hepcidin using a commercial ELISA kit (R&D systems, Minneapolis, USA) in the validation cohort.
The TIBC appeared to be a significant factor in the derivation cohort. It is known that IL-6 enhances synthesis of hepcidin and that increased hepcidin decreases serum levels of TIBC. Thus, to test for a biological plausibility, we additionally collected plasma and added measurements of hepcidin using a commercial ELISA kit (R&D systems, Minneapolis, USA) in the validation cohort.