APOLIPOPROTEIN B (APO B) AND APOLIPOPROTEIN A1 (APO A1) TESTS

What is the purpose of these tests: These tests are part of a lipid profile (total cholesterol, LDL, HDL and triglycerides). Apo B can be used as an alternative to LDL. Both can be used to evaluate one’s risk of developing cardiovascular disease.
How to prepare:
  • A blood sample must be taken.
  • Although this specific test does not usually require fasting, it is often performed at the same time as a complete lipid profile which requires fasting.
  • Refrain from drinking alcohol 24 to 48 hours before the test.
  • Refrain from engaging in strenuous exercise within 24 hours of the test.
  • Be in good health (no fever, cold, etc.).
Reference values*:

Optimal levels when the risk of cardiovascular disease is low to moderate. Used to make decisions prior to initiating treatment.

 

The risk of cardiovascular disease is greater in those with Apo B levels higher than 1.30 g/L. As a result, treatment is initiated in those whose results exceed this value.
Target values*:

Targets when being treated for hypertriglyceridemia (lifestyle changes and drugs):

  • Apo B < 0.80=””>
  • Apo B/apo A1 <>
Associated tests: These tests are seldom performed on their own. Cholesterol, LDL, HDL and triglycerides are usually measured at the same time. Other complementary tests include hs-CRP and non-HDL cholesterol. Also, as part of a complete check-up, a complete blood count is often ordered.

*Age, gender, and other cardiovascular risk factors must be taken into consideration when interpreting results. Note that values may vary between laboratories.

 

General Information

Apolipoproteins bind and transport lipids in the blood. There are two major apolipoproteins: apo B and apo A1. Apo B is found mainly in LDL particles (bad cholesterol), while apo A1 is present in HDL particles (good cholesterol).

Apo A1 and apo B measurements are ordered when it is difficult to measure HDL and LDL levels, for example, in those with elevated triglyceride levels. In such situations, apolipoprotein levels provide a better assessment of LDL concentrations which are the cause of cardiovascular diseases.

On occasion, the apo B/apo A1 ratio is calculated. The ratio is important since it helps further reduce the risk of cardiovascular disease in patients who have reached the target LDL or apo B values.

What does an abnormal test result mean?

If the result is high
A high level of apo-B is one of the main risk factors for cardiovascular disease.

Apo B levels may be high for various reasons, including:

  • Diabetes
  • Certain kidney diseases
  • Hypothyroidism
  • Liver diseases
  • Diet high in cholesterol and saturated fat
  • Smoking
  • Obesity
  • Lack of physical exercise

Some drugs can also increase Apo-B levels, these include:

  • Androgens
  • Corticosteroids (prednisone, cortisone)
  • Cyclosporine
  • Danazol
  • Certain diuretics
  • Isotretinoin
  • Progesterone
  • Sirolimus

 

If results are too low
Generally speaking, apo B values should be low (less than 1.2 g/L). An optimal target of less than 0.8 g/L is recommended for individuals with cardiovascular disease and those with a high or moderate risk of cardiovascular disease. Hyperthyroidism, malnutrition, chronic anemia, cancer or severe liver disease can lead to low apo B values.

Low apo A1 levels may play a role in cardiovascular disease.

Factors that can interfere with test accuracy

Failure to comply with test preparation, changes to one’s usual diet or recent weight loss (less than 2 weeks prior to the test), heart attack (≥ 12 weeks), trauma (surgery, viral or bacterial infection), pregnancy or recent delivery (less than 8 weeks prior to the test) can alter lipid profile results.

What you should know before going for this

Before going for a blood test, examination or other, it is always a good idea for you to have a complete list of all prescription and over the counter medications and/or natural products you may be taking. If you are unsure or have any questions, your pharmacist will be able provide you with additional information.