A coupled NAD+-peroxidase spectrophotometric assay for cholesterol.

We describe a modified enzymic reagent for determination of cholesterol and cholesterol ester in serum and in high-density lipoprotein. In this new procedure, the hydrogen peroxide produced by the action of cholesterol oxidase is used as a substrate for NAD+ peroxidase. Spectrophotometric determination of the NADH consumed in this coupled reaction provides a direct and absolute measure of the cholesterol originally present in free form and that liberated by the action of cholesterol ester hydrolase.