This test is not used as a general population screen but may be ordered if a person has a family history of heart disease and/or high cholesterol and triglycerides (hyperlipidemia). It may be performed, along with other tests, to help diagnose the cause of abnormal lipid levels, especially when someone has elevated triglyceride levels.
A health practitioner may order both an apo A-I (associated with high-density lipoprotein (HDL), the "good" cholesterol) and an apo B to determine an apo B/apo A-I ratio. This ratio is sometimes used as an alternative to a total cholesterol/HDL ratio to evaluate risk for developing CVD.
Apo B levels may be ordered to monitor the effectiveness of lipid treatment as an alternative to non-HDL-C (non-HDL-C is the total cholesterol concentration minus the amount of HDL).
In rare cases, an apo B test may be ordered to help diagnose a genetic problem that causes over- or under-production of apo B.
Apo B may be measured, along with an apo A-I or other lipid tests, when a health practitioner is trying to evaluate someone's risk of developing CVD and when a person has a personal or family history of heart disease and/or abnormal lipid levels, especially when the person has significantly elevated triglyceride levels.
Sometimes apo B is ordered to monitor a person who is undergoing treatment for high cholesterol.
Elevated levels of apo B correspond to elevated levels of LDL-C and to non-HDL-C and are associated with an increased risk of cardiovascular disease (CVD). Elevations may be due to a high-fat diet and/or decreased clearing of LDL from the blood.
Some genetic disorders are the direct (primary) cause of abnormal levels of apo B. For example, familial combined hyperlipidemia is an inherited disorder causing high blood levels of cholesterol and triglycerides. Abetalipoproteinemia, also called Apolipoprotein B deficiency or Bassen-Kornzweig syndrome, is a very rare genetic condition that can cause abnormally low levels of apo B. For more on some of these disorders, see the Related Pages tab.
Abnormal levels of apo B can also be caused by underlying conditions or other factors (secondary causes). Increased levels of apo B are seen, for example, in:
Some elevations of apo B-100 (and LDL-C) are due to mutations in the APOBgene that cause it to produce apo B-100 that is not recognized as easily by LDL receptors. Others are in the LDL receptor system of the liver cell that recognizes apo B-100. These genetic defects impede the clearing of LDL from the blood and result in accumulations of LDL in the circulation, increasing the risk of heart disease.
Chylomicrons, the lipoprotein particles that carry dietary lipids to the liver, contain a lipoprotein called apolipoprotein B-48. It is about half the size of apo B-100 and is structurally related to apo B-100. It is not considered a risk factor for atherosclerosis and is not measured as part of the apo-B test. The apo B test is specific for apo B-100.
This article was last reviewed on April 29, 2014. | This article was last modified on April 29, 2014.
The review date indicates when the article was last reviewed from beginning to end to ensure that it reflects the most current science. A review may not require any modifications to the article, so the two dates may not always agree.
The modified date indicates that one or more changes were made to the article. Such changes may or may not result from a full review of the article, so the two dates may not always agree.