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Apo A

Formal name: Apolipoprotein A-I
Related tests: HDL, LDL, Lipid Profile, Cholesterol, Apo B, Lp(a)

The Test

How is it used?

Apo A-I may be ordered, along with other lipid tests, as part of a profile to help determine your risk of developing CAD. While it is not ordered routinely, it may be helpful for patients who have a personal or family history of heart disease and/or hyperlipidemia. Apo A-I levels may also be ordered to help diagnose conditions that cause Apo A-I deficiencies and may be used to monitor the effectiveness of lifestyle changes and lipid treatments.

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When is it ordered?

Apo A-I may be measured when patients have a personal or family history of hyperlipidemia and/or premature CAD. It may be ordered when your doctor is trying to determine the cause of your hyperlipidemia and/or suspects it may be due to a disorder that is causing a deficiency in Apo A-I.

Apo A-I may be ordered along with Apo B-100 (Apo B) when your doctor wants to check your Apo A/Apo B ratio (sometimes used as a CAD risk indicator, basically showing the ratio of “good” to “bad” cholesterol).

Your doctor may order Apo A-I, along with other tests, when you have undergone lipid-lowering treatment or lifestyle changes (such as decreased dietary fat and increased regular exercise), to monitor the effectiveness of the changes.

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What does the test result mean?

Looking for reference ranges?

An increase of Apo-I is usually not a problem, but decreased levels are associated with low levels of HDL and decreased clearance of excess cholesterol from the body. Decreased levels of Apo A-I, along with increased concentrations of Apo B-100, are associated with an increased risk of coronary artery disease.

There are some genetic disorders that lead to deficiencies in Apo A-I (and therefore to low levels of HDL). People with these disorders tend to have hyperlipidemia and higher levels of low-density lipoprotein (LDL – the “bad” cholesterol). Frequently, they have accelerated rates of atherosclerosis.

Apo A-I may be decreased with:

Apo A-I may be increased with:

  • Drugs such as: carbamazepine, estrogens, ethanol, lovastatin, niacin, oral contraceptives, phenobarbital, pravastatin, and simvastatin
  • Familial hyperalphalipoproteinemia (a rare genetic disorder)
  • Physical exercise
  • Pregnancy
  • Weight reduction
  • Use of statins

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Is there anything else I should know?

The concentration of Apo A-I reflects the amount of HDL in the serum. Since women tend to have higher HDL, they also have higher levels of Apo A-I.

The Apo A-I test is not routinely ordered. Doctors still have to determine the best uses for Apo A-I and other emerging cardiac risk markers (such as Apo B-100, hs-CRP, and Lp(a)). They offer the doctor additional information in specific situations but are not meant to replace the lipid tests already routinely available.

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