Apo A
At a Glance
Why Get Tested?
To determine whether or not you have adequate levels of Apo A, especially if you have a low level of HDL-cholesterol) and to help determine your risk of developing coronary artery disease (CAD)
When to Get Tested?
When you have a high level of cholesterol or fat in the blood (hyperlipidaemia) and/or a family history of heart attack or other vascular disease; when your doctor is trying to assess your risk of developing heart disease; to monitor the effectiveness of lipid treatment and/or lifestyle changes
Sample Required?
A blood sample drawn from a vein in your arm.
Test Preparation Needed?
No test preparation is needed; however, since this test may be performed at the same time as a complete lipid profile, fasting for at least 12 hours may be required.
The Test Sample
What is being tested?
Apolipoproteins are molecules that carry cholesterol in the bloodstream as tiny particles known as lipoproteins. Apo A is an apolipoprotein that is part of the high-density lipoprotein (HDL) particle. HDL is known as the `good’ lipoprotein because it helps get rid of excess cholesterol in the bloodstream. Excess cholesterol can deposit in the arteries, causing hardening of the arteries (atherosclerosis) and, eventually, heart attacks and other vascular diseases.
If your level of Apo A is low this suggests you have a low level of `good’ HDL particles in your bloodstream. This may mean that you have a higher than normal risk of having a heart attack (coronary artery disease (CAD) or other vascular diseases.
How is the sample collected for testing?
Typically, a blood sample is obtained by inserting a needle into a vein in your arm.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed; however, since this test may be performed at the same time as a complete lipid profile, fasting for at least 12 hours may be required.
The Test
How is it used?
Apo A may be requested to help judge your risk of having a heart attack (coronary artery disease) or other vascular diseases. It is not used routinely but may be helpful in patients who have a high level of cholesterol or fat in the blood (hyperlipidaemia) or a family history of hyperlipidaemia or heart disease. An Apo A test may also be ordered to monitor the effectiveness of lifestyle changes and lipid treatments.
When is it requested?
Apo A may be requested if you have a high level of cholesterol or fat in the blood (hyperlipidaemia) or a family history of hyperlipidaemia or heart disease, particularly heart attacks at a relatively young age.
It may be requested along with an apolipoprotein B (Apo B) level if your doctor wants to check your Apo A/Apo B ratio. This basically shows the ratio of `good’ to `bad’ cholesterol.
Your doctor may order Apo A, along with other tests, to see if the level of cholesterol and fat in your blood is improving in response to medication or lifestyle changes such as eating less fatty food and exercising more.
What does the test result mean?
A low level of Apo A in the blood is associated with a low level of HDL, the `good’ cholesterol particle in the blood. This suggests your body is not getting rid of excess cholesterol well and this may increase your chance of developing a vascular disease such as coronary artery disease (heart attacks) or circulation problems in the legs.
A low level of Apo A in the blood may run in the family, eg in the inherited (genetic) condition familial hypoalphalipoproteinaemia. More commonly, Apo A is decreased due to:
- chronic renal failure
- some drugs, eg. androgens, beta blockers, diuretics, and progestins (synthetic progesterone)
- smoking
- uncontrolled diabetes.
A high level of Apo A in the blood is usually not a problem. A high level of Apo A may run in the family. More commonly, Apo A may be increased due to:
- drugs used to treat hyperlipidaemia, eg. lovastatin, simvastatin, niacin
- other drugs, eg. carbamazepine, oestrogens (including oral contraceptives)
- physical exercise
- pregnancy
- weight loss.
Is there anything else I should know?
The Apo A level in the blood reflects the amount of HDL, the `good’ cholesterol particles, in the blood. Women tend to have higher HDL, so they may also have higher levels of Apo A.
The Apo A test is not routinely used. Doctors and scientists still have to determine the best uses for Apo A. It may provide your doctor with additional information in specific situations but does not replace the lipid tests routinely available.
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