Lipoprotein B Test

Lipoprotein B (APO B)Test has been reported to be a powerful indicator of Coronary Artery Disease (CAD). In some patients with CAD, APO B is elevated even in the presence of normal LDL cholesterol.

The apolipoprotein B (apo B) test is used, along with other lipid tests, to help determine an individual's risk of developing cardiovascular disease (CVD).

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 healthcare practitioner may order both an APO A-I test (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.

Elevated levels of Lipoprotein 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 Content section.

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:

• Diabetes
• Use of drugs such as: androgens, beta blockers, diuretics, progestins (synthetic progesterones)
• Hypothyroidism
• Nephrotic syndrome (a kidney disease)
• Pregnancy (levels increase temporarily and decrease again after delivery)
   

Lipoprotein B levels may be decreased with any condition that affects lipoprotein production or affects its synthesis and packaging in the liver. Lower levels are seen with secondary causes such as:

• Use of drugs such as: estrogen (in post-menopausal women), lovastatin, simvastatin, niacin, and thyroxine
• Hyperthyroidism
• Malnutrition
• Reye syndrome
• Weight reduction
• Severe illness
• Surgery
• Cirrhosis
   

An increased ratio of Lipo B to apo A-I may indicate a higher risk of developing CVD.

Reference:

Cardiovascular event risk category cut points (optimal, moderate, high) are based on National Lipid Association recommendations- Jacobson TA et al. J of Clin Lipid. 2015; 9: 129-169 and Jellinger PS et al. Endocr Pract. 2017;23(Suppl 2):1-87