载脂蛋白（apolipoprotein，apo）是血浆脂蛋白中的蛋白质，其基本功能是运载脂类。 ApoB由于氨基酸组成的差异，可分为以下亚类：ApoB48和ApoB100。ApoB48是乳糜微粒（CM）的载脂蛋白之一；ApoB100是极低密度脂蛋白（VLDL）和低密度脂蛋白（LDL）的载脂蛋白之一。 载脂蛋白B的正常值为0.8g/L~1.1g/L。 LDL-C/apoB ratio of1.2 has been suggested to correspond to an LDL diameter of 25.5 nm, to an LDL diameter of 25.5 nm,which is the cut-off value for distinguishing LDL pattern A (large buoyant LDL) from LDL pattern B [small dense (sd)-LDL] [ 7, 8], indicating the presence of a large quantity of sd-LDL.