High-density lipoproteins (HDL) transport endogenous cholesterol from the peripheral tissues to the liver, where the cholesterol is disposed of as bile acids. Monitoring HDL levels is clinically important since an inverse relationship exists between its level and the risk of atherosclerotic disease. The Adult Treatment Panel (ATP) III of the National Cholesterol Education Program (NCEP) defines a low level as being less than 40 mg/dL. The Denka Seiken Direct HDL assay accurately measures HDL in the specimen using a two step procedure using patented technology. In the first step, non-HDL lipoproteins, including chylomicrons, VLDL, IDL and LDL, are decomposed by cholesterol esterase and cholesterol oxidase. The hydrogen peroxides produced are finally decomposed by the action of catalase. In the second step, an HDL-specific surfactant is used to release the cholesterol and similar enzymatic degradation in the presence of peroxidase to produce a measurable purple-blue color on any clinical chemistry analyzer.