Apolipoprotein B (ApoB)

Description: Apolipoprotein B is a blood test that measures that amount of Apolipoprotein B in the blood’s serum. This test is used to assess cardiovascular risk.

Also Known As: Apo B Test, Apolipoprotein B-100 Test

Collection Method: Blood Draw

Specimen Type: Serum

Test Preparation: No preparation required

When is an Apolipoprotein B test ordered?

Apolipoprotein A-I and B, as well as other lipid tests, may be ordered as part of a screening to identify a person's risk of cardiovascular disease.

Apo B is a protein that plays a role in lipid metabolism and is the major protein component of lipoproteins including VLDL and LDL, popularly known as "bad cholesterol." Apo B concentrations are similar to LDL-C concentrations.

What does an Apolipoprotein B blood test check for?

Lipids are transported throughout the bloodstream by apolipoproteins, which mix with them. Lipoproteins are held together by apolipoproteins, which protect the water-repellent lipids at their core.

Lipoproteins are cholesterol or triglyceride-rich proteins that transport lipids throughout the body for cell absorption. HDL, on the other hand, is like an empty cab. It travels to the tissues to collect excess cholesterol before returning it to the liver. Cholesterol is either recycled for future use or eliminated in bile in the liver. The only mechanism for cells to get rid of excess cholesterol is by HDL reverse transport. It protects the arteries and, if enough HDL is present, it can even reverse the formation of fatty plaques, which are deposits caused by atherosclerosis and can contribute to cardiovascular disease.

Chylomicrons are lipoprotein particles that transport dietary fats from the digestive system to tissue, primarily the liver, via the bloodstream. These dietary lipids are repackaged in the liver and combined with apo B-100 to create triglyceride-rich VLDL. This combo is similar to a taxi with a full load of passengers and apo B-100 as the driver. The taxi moves from place to place in the bloodstream, releasing one passenger at a time.

Triglycerides are removed from VLDL by an enzyme called lipoprotein lipase, which produces intermediate density lipoproteins first, then LDL. VLDL contains one molecule of apo B-100, which is kept as VLDL loses triglycerides and shrinks to become the cholesterol-rich LDL. Apo B-100 is detected by receptors on the surface of many different types of cells in the body. The absorption of cholesterol into cells is aided by these receptors.

LDL and apo B-100 transport cholesterol that is essential for cell membrane integrity, sex hormone generation, and steroid production. Excess LDL, on the other hand, can cause fatty deposits in artery walls, as well as blood vessel hardening and scarring. Atherosclerosis is a condition in which fatty deposits restrict blood arteries. The risk of a heart attack increases as the atherosclerotic process progresses.

LDL-C levels, which are typically ordered as part of a lipid profile, tend to mimic Apo B-100 levels. Many experts believe that apo B levels will eventually show to be a more accurate predictor of CVD risk than LDL-C. Others disagree, believing that vitamin B is only a modestly superior choice and that it should not be used on a regular basis. The clinical utility of apo B, as well as other developing cardiac risk markers including apo A-I, Lp(a), and hs-CRP, is still unknown.

Lab tests often ordered with an Apolipoprotein B test:

Conditions where an Apolipoprotein B test is recommended:

How does my health care provider use an Apolipoprotein B test?

An apo B/apo A-I ratio can be determined by ordering both an apo A-I and an apo B test. To assess the risk of developing CVD, this ratio is sometimes used instead of the total cholesterol/HDL ratio.

As an alternative to non-HDL-C, Apo B levels may be ordered to assess the success of lipid treatment.

An apo B test may be conducted in rare circumstances to assist determine a genetic issue that causes apo B overproduction or underproduction.

What do my Apolipoprotein B test results mean?

Raised apo B levels are linked to elevated LDL-C and non-HDL-C levels, and are linked to an increased risk of cardiovascular disease. Elevations may be caused by a high-fat diet and/or a reduction in LDL clearance from the blood.

A direct cause of abnormal apo B levels is some hereditary diseases. Familial combined hyperlipidemia, for example, is an inherited condition that causes excessive cholesterol and triglyceride levels in the blood. Apolipoprotein B deficiency, also known as Bassen-Kornzweig syndrome, is a relatively rare hereditary disorder that results in unusually low amounts of apo B.

A variety of underlying diseases and other factors might result in abnormal apo B levels.

Is apoB a heart disease risk factor? 

The markers of particle number, apoB, or LDL particle number were better at predicting the risk of heart disease than LDL-C.

There are two major forms of Apolipoprotein B, B-100 and B-48. B-100, synthesized in the liver, is the major protein in VLDL, IDL, and LDL cholesterol. B-48, synthesized in the intestines, is essential for the assembly and secretion of chylomicrons. Patients with increased concentrations of Apolipoprotein B are at increased risk of atherosclerosis.

We advise having your results reviewed by a licensed medical healthcare professional for proper interpretation of your results.