Usefulness of the total iron binding capacity in the evaluation and treatment of acute iron overdose.

The ingestion of iron-containing products is a potential toxicologic emergency. The total iron binding capacity (TIBC) has been used widely as a predictor of end-organ toxicity and a guide to the need for deferoxamine therapy. When the TIBC is greater than the serum iron concentration (SIC), it is held that no free iron is present to cause toxicity. The TIBC fails as a marker of toxicity for several reasons. First, the laboratory methods used to measure TIBC are inaccurate in the setting of iron overload. Second, the presence of deferoxamine, the antidote for iron poisoning, has been shown to make the TIBC measurement inaccurate. Third, TIBC measurements have been shown to be variable. Finally, studies and case reports demonstrate toxicity even when the TIBC is greater than the SIC. These shortcomings of the TIBC invalidate it as a predictor of toxicity in iron poisoning.