Test Details: Apolipoprotein A-I (Apo-A1) is a structural and functional protein that constitutes approximately 70% of the protein in high density lipoprotein (HDL). HDL is termed as good cholesterol in the body. Apo-A1 has specific roles in the transportation and metabolism of lipids. This test measures the amount of apo A-I in the blood. Apo A-I levels also provide more information to help evaluate CVD risk, especially when HDL levels are low.