Apolipoprotein B (apo B/Apolipoprotein B-100) is a protein that has specific roles in the transportation and metabolism of lipids and is the main protein component in LDL and VLDL . This test measures the amount of apo B in the blood. Apo B may be measured with apo A-I or other lipids. This test can be performed in Serum/heparinized or EDTA plasma.