2.3. Iron, ferritin, and transferrin levels measurement

The levels of iron, ferritin, and transferrin were measured in the serum by ELISA (Enzyme‐Linked Immunosorbent Assay) using Iron Microplate Assay Kit, Human Ferritin ELISA Kit, and Human Transferrin ELISA (MyBioSource, Southern California, San Diego, USA), respectively, following the manufacturer's specification. Absorbance was measured at 450 nm, with the correction wavelength set at 540 nm using a microplate reader. The concentration of iron, ferritin, and transferrin was calculated using linear regression analysis of absorbance values obtained for each measurement.