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)
- Uncontrolled diabetes
Apo A1 may increase with:
- Use of drugs such as: carbamazepine, estrogens, ethanol, lovastatin, niacin, oral contraceptives, phenobarbital, pravastatin, and simvastatin
- Physical exercise
- 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.