Apolipoprotein B (ApoB)

Apolipoprotein B, or ApoB for short, is a protein that can be measured along with your usual lipid panel test to determine the possibility of cardiovascular risk. It is increasingly being recommended by clinicians.

Lipoproteins (like low-density lipoprotein [also known as LDL]) in the body that contain ApoB cause atherosclerosis, the buildup of cholesterol plaque in blood vessels. Atherosclerosis causes blood vessels to narrow and harden, leading to heart attacks, strokes, and other forms of cardiovascular disease.

Typical LDL-C and ApoB levels are shown in the following table. The population % refers to the measured level from lowest (1%) to the highest (99%) LDL-C or ApoB in untreated adults in the United States:

See the figure for a representation of LDL, included to explain the difference between LDL-C, and apoB. LDL is the particle shown that carries cholesterol. LDL-C is the measured amount of cholesterol in all the LDL in the blood. ApoB is a measurement of all the ApoB in the blood. Since there is one ApoB on each LDL particle, ApoB represents the amount of LDL particles in the blood.

Image by Alex Sakers MD PhD using BioRender

Figure: this is a representation of LDL particle. Note that it contains both cholesterol and triglyceride and there is a single apoB protein on the surface of the particle. LDL particles can vary in size. Larger LDL particles carry more cholesterol. Individuals who have large LDL particles tend to have high LDL-C. Individuals who have small LDL may have normal or low LDL-C but may have many LDL particles in circulation. Since ApoB represents the number of particles and since more particles lead to higher heart disease risk, ApoB measurement is a better indicator of risk than LDL-C.

An ApoB level is a blood test that can be done at the same time as your standard cholesterol test (or alone) and shows how many of these atherosclerosis causing lipoproteins particles you have in your bloodstream.

• Adults at normal heart disease risk who are NOT being treated should have a standard lipid test every five years for routine screening.
• Children should have a standard lipid test between the ages of 9-11 and again between 17-20.
• Your clinician may recommend more frequent tests if your or your child are at increased risk for heart disease, stroke, or other complications, or as part of regular treatment monitoring.

Much like the importance of lowering your LDL-C, patients with high ApoB, particularly patients at higher risk for heart disease, should work with their clinician to lower their ApoB level through diet and lifestyle and medications, where appropriate. The same medications used to lower LDL-C are effective in lowering ApoB levels.