16 Because of the unreliability of the measured TIBC, this measurement is neither a useful nor a clinically indicated laboratory test in the evaluation of iron poisoning.Ī. Another study demonstrated that even though the TIBC increased and remained above the serum iron concentration in patients with iron ingestions, symptoms of iron toxicity still occurred. 25 This same study showed that TIBC determinations varied substantially among different laboratories. 23, 24 An in vitro study demonstrated that adding iron to pooled serum resulted in an artifactual rise in the TIBC. Also, TIBC measurements may be unreliable in the presence of excess serum iron or deferoxamine. No data have shown that iron toxicity only occurs when the serum iron concentration exceeds the TIBC. However, clinical experience has shown this maxim is untrue. This was based on the assumption that the binding of iron to plasma proteins prevents any toxicity-when a serum iron concentration is less than the TIBC, there is little risk for toxicity. In the past, a serum iron concentration that exceeded the TIBC was considered an indication for chelation therapy and was believed to be a necessary laboratory test in the evaluation of the patient with iron poisoning. LIEBELT MD, in Haddad and Winchester's Clinical Management of Poisoning and Drug Overdose (Fourth Edition), 2007 TOTAL IRON-BINDING CAPACITY TIBC may be increased in some animals with iron overload ( House et al., 1994 Sprague et al., 2003) and in dogs with chronic hepatopathy ( Soubasis et al., 2006).ĮRICA L. A slight increase in serum TIBC was reported in an experimental study of diet-induced iron deficiency anemia in young growing dogs ( Fry and Kirk, 2006), but serum TIBC is generally normal in dogs with naturally occurring iron deficiency anemia ( Harvey et al., 1982 Weiser and O'Grady, 1983). Serum TIBC is low-normal or decreased in association with inflammatory disorders ( Feldman et al., 1981b Ottenjann et al., 2006 Smith and Cipriano, 1987) and increased in iron-deficient humans, rabbits, pigs, horses, and cattle ( Furugouri, 1972 Halvorsen and Halvorsen, 1973 Harvey et al., 1987a Miltenburg et al., 1992b Mollerberg et al., 1975). The percentage saturation of transferrin with iron is calculated by dividing the serum iron concentration by the TIBC and multiplying by 100. TIBC is calculated by measuring serum iron and serum unsaturated iron-binding capacity and summing these values. The total iron-binding capacity (TIBC) of serum is a measure of total serum transferrin (apotransferrin, monotransferrin, diferric transferrin) concentration because insignificant amounts of plasma iron are bound to other proteins. Harvey, in Clinical Biochemistry of Domestic Animals (Sixth Edition), 2008 C Serum Total Iron-Binding Capacity
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