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​Apolipoprotein B (also called apolipoprotein B-100 or apo B) is a protein that is involved in the metabolism of lipids and is the main protein constituent of lipoproteins such as very low-density lipoprotein (VLDL) and low-density lipoprotein (LDL, the "bad cholesterol"). This test measures the amount of apo B-100 in the blood.

Test at a glance

Clinical Utility
​The apo B test can be used as an alternative to a standard lipid panel to evaluate a patient's risk of developing cardiovascular disease (CVD); sometimes to help monitor treatment for high LDL cholesterol or to help diagnose a rare inherited apo B-100 deficiency.

Ordering
​On the requisition form, enter ‘Apo B’ in the ‘Other Tests’ section. 

Patient instructions
​A simple blood sample is required and can be collected at any LifeLabs patient service centre.  There are no special instructions; however, this test is often ordered at the same time as other tests that require fasting, so patients may be instructed to fast for 12 hours prior to having this test.

Turnaround Time
​Test results will be available within 2 days.

Cost
​This test is not currently covered by provincial health insurance plans, but may be covered by extended health insurance plans. Contact us to find out about the current fee for the test.

Cautions
​No test preparations are needed.

Healthcare Professional Information

​Apolipoproteins combine with lipids to transport them throughout the bloodstream. Apolipoproteins provide structural integrity to lipoproteins and shield the water-repellent (hydrophobic) lipids at their centre. Most lipoproteins are cholesterol- or triglyceride-rich and carry lipids through the body for uptake by cells.

Chylomicrons are the lipoprotein particles that carry dietary lipids from the digestive tract, via the bloodstream, to tissue—mainly the liver. In the liver, the body repackages these dietary lipids and combines them with apo B-100 to form triglyceride-rich VLDL.

An enzyme called lipoprotein lipase (LPL) removes triglycerides from VLDL to produce intermediate density lipoproteins (IDL) first and then LDL. Each VLDL particle contains one molecule of apo B-100, which is retained as VLDL loses triglycerides and shrinks to become the more cholesterol-rich LDL. Apo B-100 is recognized by receptors found on the surface of many of the body's cells. These receptors promote the uptake of cholesterol into the cells.

The cholesterol that LDL and apo B-100 transport is vital for cell membrane integrity, sex hormone production, and steroid production. In excess however, LDL can lead to fatty deposits (plaques) in artery walls and lead to hardening and scarring of the blood vessels. These fatty depositions narrow the vessels in a process termed atherosclerosis. The atherosclerotic process increases the risk of heart attack.

Patient Frequently Asked Questions(FAQs)

​How is it used?

To help evaluate your risk of developing cardiovascular disease (CVD); and sometimes to help monitor treatment for high cholesterol or to help diagnose a rare inherited apo B-100 deficiency.

When to get tested?

When you have a personal or family history of heart disease and/or high cholesterol and triglyceride levels and your doctor is trying to determine your risk of developing CVD; sometimes on a regular basis when you are being treated for high LDL-cholesterol (LDL-C); rarely when your doctor suspects that you have an inherited apo B-100 deficiency.

How is it used?

Apo B-100 is a protein that is involved in the metabolism of lipids and is the main protein constituent of lipoproteins such as very low-density lipoprotein (VLDL) and low-density lipoprotein (LDL, the "bad cholesterol"). Concentrations of apo B-100 tend to mirror those of LDL-C.

The apo B test is used, along with other lipid tests, to help determine an individual's risk of developing CVD.

This test may be a more reliable indicator of CVD than LDL-C and it may be performed, along with other tests, to help diagnose the cause of abnormal lipid levels, especially when a patient has elevated triglyceride levels.

In some situations, apo B-100 testing may be used in conjunction with LDL-C testing to determine if pharmacotherapy should be initiated.

Apo B levels may be ordered to monitor the effectiveness of lipid treatment as an alternative to LDL-C.

In rare cases, an apo B test may be ordered to help diagnose a genetic problem that causes over- or under-production of apo B-100.

When is it ordered?

Apo B-100 may be measured, along with other lipid tests, when a doctor is trying to evaluate a patient's risk of developing CVD and when a patient has a personal or family history of heart disease and/or abnormal lipid levels, especially when the patient has significantly elevated triglyceride levels.

Sometimes an apo B test is ordered to monitor a patient undergoing treatment for high LDL cholesterol.

What does the test result mean?

Elevated levels of apo B-100 correspond to elevated levels of LDL-C and to non-HDL-C and are associated with an increased risk of CVD. Elevations may be due to a high-fat diet and/or decreased clearing of LDL from the blood.

Some genetic disorders are the direct (primary) cause of abnormal levels of apo B-100. For example, familial combined hyperlipidemia is an inherited disorder causing high blood levels of cholesterol and triglycerides. Abetalipoproteinemia, also called Apolipoprotein B deficiency or Bassen-Kornzweig syndrome, is a very rare genetic condition that can cause abnormally low levels of apo B-100.

Abnormal levels of apo B-100 can also be caused by underlying conditions or other factors (secondary causes). For example, increased levels of apo B-100 are seen with:

  • Diabetes
  • Use of drugs such as: androgens, beta blockers, diuretics, progestins (synthetic progesterones)
  • Hypothyroidism
  • Nephrotic syndrome (a kidney disease)
  • pregnancy (levels increase temporarily and decrease again after delivery)
Apo B-100 levels may be decreased with any condition that affects lipoprotein production or affects its synthesis and packaging in the liver. Lower levels are seen with secondary causes such as:
  • Use of drugs such as: estrogen (in postmenopausal women), lovastatin, simvastatin, niacin, and thyroxine
  • Hyperthyroidism
  • Malnutrition
  • Reye's syndrome
  • Weight loss
  • Severe illness
  • Surgery
  • Cirrhosis

Is there anything else I should know?

Some elevations of apo B-100 (and LDL-C) are due to mutations in the apoB gene that cause it to produce apo B-100 that is not recognized as easily by LDL receptors. Others are in the LDL receptor system of the liver cell that recognizes apo B-100. These genetic defects impede the clearing of LDL from the blood and result in accumulations of LDL in the circulation, increasing the risk of heart disease.

Chylomicrons, the lipoprotein particles that carry dietary lipids to the liver, contain a lipoprotein called apolipoprotein B-48. It is about half the size of apo B-100 and is structurally related to apo B-100. It is not considered a risk factor for atherosclerosis and is not measured as part of the apo B test. The apo B test is specific for apo B-100.

Is there a charge for the test?

This test is not currently covered by provincial health insurance plans, but may be covered by your extended health insurance plan. Contact us to find out about the current fee for the test.

Note: Content on this page has been used and adapted with permission from Lab Tests Online.

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