Comparison of 8 Different Colorimetric, Radiochemical and Immunological Procedures for the Determination of Iron Binding Capacity

(Eingegangen am 22. August/29. Oktober 1973) Two radiochemical (Irosorb 59 and Res-O-Mat Fc59), a mechanized (DSA 560) and several manual colorimetric procedures (test combination of Roche, Merck and Haury) for the determination of the total iron binding capacity were compared with the transferrin-binding capacity (immunoprecipitation). Whereas all methods show a satisfactory correlation with the transferrin concentration, most colorimetric procedures lead to higher values, while the Merckotcst leads to lower values for the total iron binding capacity. In some control sera the total iron binding capacity is overestimated by several colorimetric methods, which are also subject to interference by hemoglobin. All other procedures are unaffected by hemolysis. With the mechanization of procedures for immunoprecipitation, these methods are now to be preferred. Zwei radiochemische (Irosorb 59 und Res-O-Mat Fe59), ein mechanisiertes (DSA 560) und verschiedene manuelle kolorimetrische Verfahren (Testkombination von Roche, Merck und Haury) zur Bestimmung der totalen Eisenbindungskapazitat werden mit der Transferrin-Bindungskapazitat (Immunoprazipitation) verglichen. Wahrend alle Methoden mit der Transferrin-Konzentration ausreichend korrelieren, fuhren die meisten kolorimetrischen Verfahren zu hoheren und der Merckotest zu niedrigeren Werten fur die totale Eisenbindungskapazitat. In einigen Kontrollseren wird die totale Eisenbindungskapazitat mit verseiliedenen kolorimetrischen Methoden zu hoch gefunden. Die selben werden durch Hamoglobin gestort. Alle anderen Verfahren werden durch Hamolyse nicht beeinflust. Mit der Einfuhrung von mechanisierten Verfahren zur immunologischen Transferrin-Bestimmung sollte diese Methode bevorzugt werden. The total iron binding capacity of human serum is considered to be a useful estimation of its transferrin concentration. However, recent investigations by various authors (1 —3), have shown, that in addition to transferrin, other serum proteins are able to bind a small quantity of iron ions. Therefore, the total iron binding capacity is expected to exceed the transferrin iron binding capacity if iron is added under saturating conditions. In the following, this assumption was investigated with various procedures for the determination of the total iron binding capacity in human sera. Usually one third of the iron binding capacity of serum is loaded with iron. After the addition of labelled iron, the latent iron binding capacity1) can be calculated from the ratio of bound to added