The Apolipoprotein A1 (Apo A1) test measures the level of Apo A1 protein in the blood. Apo A1 is the main protein component of High-Density Lipoprotein (HDL), commonly known as “good cholesterol.” It plays a key role in removing excess cholesterol from tissues and blood vessels and transporting it to the liver for elimination. 

 The Apolipoprotein B (Apo B) test measures the level of apolipoprotein B in the blood. Apo B is a key protein found on the surface of atherogenic lipoproteins, including LDL (bad cholesterol), VLDL, IDL, and lipoprotein(a). Each of these particles contains one Apo B molecule, making Apo B a reliable indicator of the total number of cholesterol-carrying particles that can contribute to plaque formation in arteries.