The CDC method for HDL-C includes three processes: Ultracentrifugation, precipitation by heparin-manganese, and which method?

• A. Abell-Kendall Method
• B. Friedewald calculation
• C. Direct enzymatic assay
• D. Cholesterol esterification assay

Answer: (A)

The key idea is how HDL-C is measured after separating non-HDL lipoproteins. In the CDC HDL-C method, you first use ultracentrifugation to remove the triglyceride-rich particles and separate lipoproteins by density. Then you precipitate the remaining non-HDL particles with heparin–manganese, leaving the HDL fraction in solution. The amount of cholesterol in that HDL-enriched fraction is then quantified with a direct enzymatic assay. This enzymatic approach uses cholesterol esterase to liberate cholesterol, cholesterol oxidase to produce a detectable product, and peroxidase with a chromogenic substrate to give a color change that correlates with HDL-C concentration.

Abell-Kendall is an older chemical method for measuring cholesterol and is not the final quantification step used after HDL isolation in this CDC protocol. The Friedewald calculation estimates LDL-C from measured total cholesterol, HDL-C, and triglycerides, rather than providing the HDL-C measurement itself. The cholesterol esterification concept isn’t the specific method used for the HDL-C readout in this workflow.