Intended use

Immunoassay for the in vitro quantitative determination of ferritin in human serum.

Summary

Ferritin is a macromolecule with a molecular weight of at least 440 kD (depending on the iron content) and consists of a protein shell (apoferritin)of 24 subunits and an iron core containing an average of approx.2500 Fe3+ ions (in liver and spleen ferritin). (1) Ferritin tends to form oligomers, and when it is present in excess inthe cells of the storage organs there is a tendency for condensation to semicrystalline hemosiderin to occur in the lysosomes.At least 20 isoferritins can be distinguished with the aid of isoelectric focusing. (2)This microheterogeneity is due to differences in the contentsof the acidic H and weakly basic L subunits. The basic isoferritinsare responsible for the long-term iron storage function, and are foundmainly in the liver, spleen, and bone marrow. (1, 3) Acidic isoferritins are found mainly in the myocardium, placenta, andtumor tissue. They have a lower iron content and presumably function as intermediaries for the transfer of iron in various syntheses (4, 5, 6) The determination of ferritin is a suitable method for ascertaining theiron metabolism situation. Determination of ferritin at the beginningof therapy provides a representative measure of the body’s ironreserves. A storage deficiency in the reticulo-endothelial system(RES) can be detected at a very early stage (7) Clinically, a threshold value of 20 μg/L (ng/mL) has proved useful inthe detection of prelatent iron deficiency. This value provides a reliable indication of exhaustion of the iron reserves that can be mobilized for hemoglobin synthesis. Latent iron deficiency is defined as a fall below the12 μg/L (ng/mL) ferritin threshold. These two values necessitate no further laboratory elucidation, even when the blood picture is still morphologically normal. If the depressed ferritin level is accompanied by hypochromic, microcytal anemia, then manifest iron deficiency is present. (1) When the ferritin level is elevated and the possibility of a distribution disorder can be ruled out, this is a manifestation of iron overloading in the body.400 μg/L (ng/mL) ferritin is used as the threshold value. Elevated ferritin values are also encountered with the following tumors: acute leukemia, Hodgkin’s disease and carcinoma of the lung, colon, liver and prostate. The determination of ferritin has proved to be of value in liver metastasis. Studies indicate that 76 % of all patients with liver metastasis have ferritin values above 400 μg/L (ng/mL). Reasons for the elevated values could be cell necrosis, blocked erythropoiesis or increased synthesis in tumor tissue.Two monoclonal mouse antibodies - M-4.184 and M-3.170 - are usedto form the sandwich complex in the assay.

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