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Colorimetry of iron in serum with Ferrozine (as used in the Technicon SMAC) or with bathophenanthroline (as used in the Du Pont aca) is influenced by EDTA, in contrast to such measurements with atomic absorption spectroscopy. Therefore EDTA contamination should be avoided with these colorimetric methods. If, however, contamination with EDTA is suspected, addition of zinc sulfate to serum or to the SMAC "ascorbic acid reagent" will cancel the influence of EDTA on measurements of iron in the SMAC.

We used a commercial enzymatic kit for measuring 7 alpha-hydroxylated bile acids to screen urines from normal subjects, liver-transplant recipients, and patients with various liver diseases, cerebro-hepato-renal syndrome, or cerebrotendinous xanthomatosis (CTX). Because of their high concentrations of 7 alpha-hydroxylated compounds excreted, the CTX patients were clearly distinguished from all other groups except for a slight overlap with the patients with cerebro-hepato-renal syndrome and liver-transplant recipients. Gas chromatography for bile alcohols completed the differential diagnosis.