Direct Determination and Binding Capacity of Serum Iron

Abstract

Abstract A modified direct procedure is described for measuring serum iron (SI) levels and serum unsaturated iron-binding capacities (UIBC). Protein digestion or precipitation, as well as extraction of the color of the iron complex are eliminated. The protein-bound iron is dissociated at acid pH, reacted with terpyridine in the ferrous state, and the optical density is read at 552 mµ. The UIBC is measured by incubating the serum at alkaline pH with a known excess of iron. Only the unbound excess reacts with terpyridine, and the UIBC is obtained by difference. The mean normal SI level found was 98.0 µg./100 ml. with a range of 44-155; mean UIBC was 243, with a range of 150-336; mean total IBC was 344, with a range of 251-437. Seven other investigators report higher mean SI levels, varying from 110 to 173; UIBC values are in better agreement. SI levels as low as 8 µg./100 ml. in anemia were measured. The desirability of carrying out both determinations is indicated by the fact that 18 per cent of patients had normal SI levels, but abnormal UIBC. The amount of iron bound to conalbumin, the iron-binding protein from egg white used as a control for the UIBC determination, agreed with that determined by other investigators.