Determination of ferritin in urine and in serum of normal adults with a sensitive enzyme immunoassay.

We have determined ferritin in both urine and serum of normal subjects by means of a sensitive sandwich-type enzyme immunoassay method. The assay system consisted of an antibody Fab'-beta-D-galactosidase conjugate and an antibody F(ab')2-immobilized solid phase. The lowest concentrations of ferritin detectable with the present method were 0.2 and 1 ng/ml in urine and in serum, respectively. There was a high correlation between the levels of ferritin in urine and those in serum (r = 0.79), and the geometric mean level in urine of normal males (4.1 ng/ml) was significantly higher than that of normal females (1.8 ng/ml) as was observed in their corresponding levels in serum. These results indicate that urine ferritin in normal subjects may also reflect body iron stores, and that the assay of urine ferritin may provide a useful means of evaluating iron stores.