In LDL homogeneous assay, which component is measured enzymatically after separation?

• A. Cholesterol
• B. LDL particle number
• C. Triglyceride
• D. HDL

Answer: (A)

In an LDL homogeneous assay, the goal is to quantify the cholesterol content specifically within LDL particles after separating LDL from other lipoproteins. The enzymatic reaction sequence starts with cholesterol esterase converting cholesteryl esters to free cholesterol, followed by cholesterol oxidase producing hydrogen peroxide. In the presence of a chromogenic substrate and peroxidase, the hydrogen peroxide generates a color change. The intensity of this color correlates with the amount of cholesterol present in LDL, not with the number of LDL particles, triglyceride levels, or HDL content. Therefore, the component measured enzymatically is cholesterol.