Steroid interference in iron-cholesterol reactions: a comparative study.

Interference from various physiological and non-physiological steroids in the spectrophotometric determination of cholesterol by the Zak method (ferric chloride) and the method of Parekh and Jung (ferric acetate) was quantitatively measured. Contribution of the steroids at the specific absorption maxima of the cholesterol assays was determined by employing the steroids (40 mg/dl) alone, or added to a serum pool of known cholesterol content. The results show that the method of Parekh and Jung is less influenced by the presence of steroids than the Zak method. Observations on the structural specificity of the iron-cholesterol reaction are discussed.