Determination of ferritin in serum and in synovial fluids of patients with rheumatoid arthritis

Ferritin in sera and in synovial fluids were determined by method of immunoradiometric assay (IRMA) and of radioimmunoassay (RIA). These methods have been proved to be reproducible. The coefficient variation was 7.4 to 9.9% in IRMA and 5.6 to 8.0% in RIA. There were a good correlation between methods of IRMA and of RIA (r=0.989). The mean recovery rate of ferritin in serum was 101.2% in IRMA and 101.0% in RIA, respectively. The determination of serum ferritin revealed a 16% reduction in average after preservation at -20℃ during over 100 days. The levels of serum ferritin in healthy controls were 131.4±52.1 ng/ml in 34 males and 58.4±39.9 ng/ml in 38 females. The sex differences were statisticalIy significant (p