Modified aca method for determination of iron chelated by deferoxamine and other chelators

Iron in serum and urine specimens containing deferoxamine (a chelator used in treating acute iron intoxication) can be measured by the DuPont aca discrete-analyzer method for iron if 0.5 mL of a 100 mL/L solution of thioglycolic acid (mercaptoacetic acid) is added to the IRN-1 and IRN-2 test packs before their use. This reagent releases the unreactive chelated iron, allowing reliable colorimetry. Because about 50% of hemoglobin iron is measured by the modified method, hemolysed samples should not be used (or results should be corrected for hemoglobin iron). The modification allows emergency determination to total serum iron and assessment of urinary iron during chelation therapy, as well as measurement of plasma iron in samples treated with sodium citrate or oxalate plus fluoride (the unmodified aca iron method gives falsely low iron values in the presence of these chelators). About 60% of iron present as the dextran complex (Imferon) is measured by the modified aca method, as compared with <5% by the unmodified aca technique.