The total iron-binding capacity in iron poisoning. Is it useful?

Traditionally, a serum iron concentration in excess of the total iron-binding capacity (TIBC) is considered as an indication for deferoxamine therapy in acute iron poisoning. We observed a reversible elevation of the TIBC in patients with iron poisoning that coincided with their acute hyperferremia and have hypothesized that this is a laboratory aberration. We tested this hypothesis in vitro and found that the addition of iron to test serum samples produced a related increase in the TIBC, and alteration of the assay by providing additional adsorbent prevented this occurrence. We also evaluated the reproducibility of the TIBC as performed by 500 laboratories on 10 different reference samples. The mean coefficient of variation was 16%, which was unsatisfactory. We concluded that the TIBC should not be used in the decision for the initiation of deferoxamine therapy in acute iron poisoning. Furthermore, high TIBC values that are occasionally seen in patients with iron poisoning should not be considered as providing a protective effect.