[Measurement of serum ferritin by solid-phase enzyme immunoassay: results in normal female subjects of various ages (author's transl)].

Determination of ferritin in serum is valuable for assessing the body iron stores. We have developed a sandwich type enzyme immunoassay for ferritin in human serum and measured serum ferritin concentrations in 179 presumably normal female subjects aged 20 to 88 years. 1) An antibody F (ab')-immobilized solid-phase was first allowed to react with ferritin and then the antibody Fab'-beta-D-galactosidase complex was reacted with the ferritin on the solid-phase. The enzymatic activity bound to the solid-phase was measured by use of 4-methylumbelliferyl beta-D-galactoside as a substrate. 2) An useful range of the assay was from 1 to 100 ng/ml, and the assay was as sensitive as radioimmunoassay. Analytical recoveries of various amounts of ferritin were in the range of 95 to 100%. Between-assay and within-assay coefficients of variation were less than or equal to 12%. The correlation coefficients between values determined by our enzyme immunoassay and two commercially available radioimmunoassay kits (SPAC, GammaDab) were both 0.97. 3) Logarithmic mean values (+/- ISD) of serum ferritin determined by our enzyme immunoassay in 160 normal female subjects were as follows: women 20 to 49 years old, 18.9 (9.2-38.7) ng/ml; women 50 to 59 years old, 36.1 (15.5-84.2) ng/ml; women over 60 years old, 59.2 (31.7-110.8) ng/ml. Twenty six percent of the female subjects aged 20 to 49 years an six percent aged over 60 years showed less than 10 ng/ml levels of serum ferritin, indicating the deficiency of storage iron.