The value of the serum iron (SI) and the total iron-binding capacity (TIBC) of the serum in hematologic diagnosis has resulted in numerous publications and has been reviewed recently by several authors.1-4 The methods employed for the determination of the serum TIBC have been: (a) intravenous injection of iron,5-9 (b) "optical" methods,7,10-12 (c) "iron excess" procedures which quantitate either the excess unbound iron 13-19 or the bound iron by colorimetric * or isotopic 22,26,28,29 techniques after removal of the excess iron by resins,23,25,26,2,28,29 magnesium carbonate,24,27,30,32,33 or other means.20,21,31
Intravenous injection of iron can be accompanied by local and systemic untoward reactions, and the "optical" methods have also had several disadvantages: (1) they require relatively large quantities of serum which must be free of interfering pigments and turbidity; (2) serum usually cannot be stored beyond 24 hours at refrigerated temperatures; and (3) the incremental procedures, in