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​Apolipoprotein A1 (apo A1) is a protein that has a specific role in the metabolism of lipids and is the main protein component in high-density lipoprotein (HDL, the "good cholesterol"). This test measures the amount of apo A1 in the blood.

Test at a glance

Clinical Utility
​The apo A1 test helps diagnose inherited or acquired conditions that cause apo A1 deficiencies.

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

Patient instructions
​A simple blood sample is required and can be collected at any LifeLabs patient service centre. Patients should 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 throughout the body for uptake by cells. HDL goes out to the tissues and picks up excess cholesterol, then transports it back to the liver. In the liver, the cholesterol is either recycled for future use or excreted into bile. HDL's reverse transport is the only way that cells can get rid of excess cholesterol. It helps protect the arteries and, if there is enough HDL present, it can even reverse the build-up of fatty plaques, deposits resulting from atherosclerosis that can lead to cardiovascular disease (CVD).

Apolipoprotein A activates the enzymes that load cholesterol from the tissues into HDL and allows HDL to be recognized and bound by receptors in the liver at the end of the transport. There are two forms of apolipoprotein A: apo A1 and apo A2. Apo A1 is found in greater proportion than apo A2 (about three to one). The concentration of apo A1 can be measured directly and tends to rise and fall with HDL levels. Deficiencies in apo A1 correlate with an increased risk of developing CVD.

Patient Frequently Asked Questions(FAQs)

​How is it used?

Apo A1 is a protein that has a specific role in the metabolism of lipids and is the main protein component in HDL, the "good cholesterol". HDL removes excess cholesterol from cells and takes it to the liver for recycling or disposal. Levels of apo A1 tend to rise and fall with HDL levels, and deficiencies in apo A1 correlate with an increased risk of developing CVD.

When is it ordered?

Apo A1 may be measured when a patient has a personal or family history of abnormal lipid levels and/or premature CVD. It may be ordered when a doctor is trying to determine the cause of a patient's high cholesterol and/or suspects it may be due to a disorder that is causing a deficiency in apo A1.

What does the test result mean?

There are some genetic disorders that lead to deficiencies in apo A1 (and therefore to low levels of HDL). People with these disorders tend to have abnormal lipid levels, including high levels of low-density lipoprotein (LDL, the "bad" cholesterol). Frequently, they have accelerated rates of atherosclerosis. These genetic disorders are primary causes of low apo A1.

Changes in levels of apo A1 may also be associated with other factors. Some of the conditions that contribute to decreases, or increases, in apo A1 are listed below.

Apo A1 may decrease with:

  • Chronic kidney disease
  • Use of drugs such as: androgens, beta blockers, diuretics, and progestins (synthetic progesterone)
  • Smoking
  • Uncontrolled diabetes
  • Obesity

Apo A1 may increase with:

  • Use of drugs such as: carbamazepine, estrogens, ethanol, lovastatin, niacin, oral contraceptives, phenobarbital, pravastatin, and simvastatin
  • Physical exercise
  • Pregnancy
  • Weight loss
  • Use of statins

Is there anything else I should know?

The apo A1 test is not routinely ordered. Doctors still have to determine the best uses for the apo A1 and other tests for emerging cardiac risk markers —for example, apo B, hs-CRP, and Lp(a). They offer additional information in specific situations but are not meant to replace the lipid tests already routinely available.

The concentration of apo A1 reflects the amount of HDL in the serum. Since women tend to have higher HDL, they also have higher levels of apo A1.

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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