Relation between iron content of serum ferritin and clinical status factors extracted by factor analysis in patients with hyperferritinemia

The aims of this study were to develop a new technique for determination of iron content of serum ferritin (ICF, μmol Fe/mg protein) and to investigate relations between ICF and clinical status in patients with hyperferritinemia. Methods ICF values were determined by a combination of immunoprecipitation of ferritin and direct colorimetric iron assay. One hundred fifty patients with hyperferritinemia were screened. Factor analysis of the results of 11 laboratory tests was applied to extract factors representing the clinical status of patients. Relations between the extracted factors and the ICF values or serum ferritin concentrations were assessed. Results Within-run coefficients of variation (CVs) of the ICF assay were 5.7%. The mean ICF value of 150 patients was 0.423 μmol/mg (SD, 0.211 μmol/mg). Three factors representing clinical status were identified: inflammation, tissue cell damage, and body iron status. Serum ferritin level correlated with all three factors. In contrast, ICF correlated significantly only with the factor representing tissue cell damage (r = 0.293, p = 0.001), and this correlation was independent of inflammation and iron status (p = 0.008). Conclusions ICF changes in response to tissue cell damage independent of inflammatory and body iron statuses, whereas serum ferritin changes in response to all three pathologic statuses.