Apolipoprotein B

Apolipoprotein B Blood Test measures the amount Apolipoprotein B in the blood. This test helps to determine the risk for heart disease.

What is Apolipoprotein B?

Apolipoprotein B or Apo B is a protein present in the body. It is the main protein component of low-density lipoprotein (LDL, the bad cholesterol) and very low-density lipoprotein (VLDL).

Lipids cannot dissolve in blood by itself. Apolipoproteins combine with lipid to form lipoproteins and help in the transport of lipids throughout the bloodstream. Lipoproteins are spherical in structure and are of four (4) types. Each type of lipoprotein has its own characteristic protein and lipid composition. They are the high-density lipoprotein (HDL), low-density lipoprotein (LDL), very low-density lipoprotein (VLDL), and chylomicrons.

Chylomicrons are lipoproteins that carry dietary lipids to the liver. In the liver, these dietary lipids combine with Apo B to form triglyceride-rich VLDL. This combination is then transported across the bloodstream releasing lipids.

Lipoprotein lipase is an enzyme that helps to remove triglycerides from VLDL. As VLDL gets free off of triglycerides, it becomes intermediate-density lipoprotein (IDL) first and then LDL. The more cholesterol-rich LDL that are formed are transported across the body. Apolipoprotein B is the major protein for the low-density lipoprotein and helps in its transport. It helps the LDL to bind with receptors in the cells and promote the uptake of cholesterol into the cells. This results increased levels of cholesterol in the body. If there are high levels of LDL in the body, it results in the build-up of fatty plaques or deposits in the blood vessels.

Assessing the levels of Apolipoprotein B directly reflects the low-density lipoprotein levels. Therefore high levels of Apolipoprotein B in the blood may increase the risk of cardiovascular diseases (heart diseases).

Why this test is performed?

This test is performed to determine whether you have normal or abnormal levels of Apolipoprotein B in the blood. Your doctor may ask to perform this test if you have a family history of cardiovascular diseases or if you are at risk of developing cardiovascular diseases. This test is also recommended if you have an abnormal level of low-density lipoprotein (LDL).

You may be advised to perform this test to diagnose the cause of abnormal lipid levels, especially when someone has elevated triglyceride levels. This test is recommended to monitor the effectiveness of treatment in individuals receiving treatment for high cholesterol. This test is also performed if your doctor suspects that you have an inherited apo B deficiency.

How often this test is performed?

If you have a family history of cardiovascular diseases (heart diseases) your doctor may ask to perform this test in a 6 monthly or a yearly basis. If you are diagnosed with cardiovascular diseases (heart diseases), then you may have to perform this test on a regular basis as instructed by the doctor.

Precautions:

Certain medicines such as androgens, beta blockers, diuretics, progestins, and estrogen may affect the test results. Inform the healthcare provider about all the medications you take before the test.

If the test results show high levels of Apo- B than the normal range it may indicate the risk of cardiovascular diseases. High levels of Apo- B along with high levels of LDL (Bad cholesterol) indicates an increased risk of cardiovascular disease.

High levels of Apo- B are also seen in individuals with diabetes, hypothyroidism or chronic kidney disease. Individuals with an inherited disorder called familial combined hyperlipidemia (high cholesterol and triglyceride levels) may also show increased Apo-B levels in the blood.

Pregnant women may also show high levels of Apo-B in the blood. Individuals who are taking medicines such as androgens, beta blockers, diuretics, progestins may also show increased levels of Apo- B in the blood.

Low levels of Apo- B than the normal range are seen in individuals with hyperthyroidism, liver cirrhosis, malnutrition, severe illness, or Reye syndrome (a condition of swelling in the brain and liver damage). Individuals who had undergone surgery and who take medicines such as estrogen may also show low levels of Apo-B in the blood.

Individuals with a rare genetic condition Abetalipoproteinemia also called Apolipoprotein B deficiency may also show very low levels of Apo-B in the blood.

Based on the test results, your doctor may advise appropriate medical treatments, lifestyle modifications, or further diagnostic tests.