Definition

The Apo B or apolipoprotein B-100 test is a blood test that provides information on a person's risk of cardiovascular disease, which affects the heart and blood vessels. This test measures the level of serum Apo B, a protein that transports substances in the bloodstream that contribute to plaque formation, a fatty deposit that has the potential to obstruct the arteries. 

Apolipoprotein B facilitates the transportation of lipids to their intended destinations and distributes them throughout the circulatory system. However, it exclusively transports lipids that are notorious for their negative image, namely low-density lipoprotein (LDL), very low-density lipoprotein (VLDL), and other similar lipids. These lipoproteins are referred to as "bad" cholesterols due to their potential to harm the heart and arteries when present in excessive quantities.

Apo B tests are frequently requested in conjunction with LDL cholesterols tests as a component of a lipid profile. There is a consensus among many experts that apo B test may ultimately surpass LDL cholesterols test as a better risk indicator of cardiovascular disease. 

It is suggested to evaluate apo B as a means of improving risk prediction in individuals with numerous cardiovascular risk factors. Contrary to this viewpoint, a number of experts hold the opinion that apo B is only slightly superior and do not advise using it as a routine test. The clinical value of apo B and other growing cardiac risk markers, such as apo A-I, Lp(a), and hs-CRP, has not been completely demonstrated.

We also have an article on LDL which you can read here: LDL - Definition, Indication and Contraindication.

Indication

In conjunction with other lipid tests, the apo B test is utilized to assess the CVD risk of an individual. This test is not employed as a routine screening test for the general population. Generally, it may be requested by a doctor if an individual has a family history of heart disease and/or hyperlipidemia (elevated levels of lipids in the blood, such as cholesterol and triglycerides). When an individual is found to have high triglyceride levels, apo B test may be carried out with other tests to aid in the diagnosis of abnormal lipid levels.

This test may also be carried out to assess the effectiveness of lipid-lowering medicine treatment. Occasionally, apo B test could be performed to aid in the diagnosis of a hereditary condition that results in excessive or insufficient production of apo B.

It is common that apo B test is performed together with apo A-I test. The apo B/apo A-I ratio is sometimes used as an alternative to the total cholesterol/HDL ratio in a lipid profile to evaluate one's likelihood of developing cardiovascular disease.

Contraindication

There are no individuals for whom it is advised against to check their serum apo B level; everyone is eligible to undergo blood tests for monitoring the levels of apo B in their bodies.

Preparations Prior to Test

Although overnight fasting may not be necessary to evaluate apo B levels, it is frequently recommended to fast for a minimum of twelve hours if this test is carried out alongside other tests that do require fasting, such as LDL cholesterol, HDL cholesterol, and triglycerides tests.

Certain medications and habits have the potential to affect the test's outcome. It is advisable to inform your physician about your eating habits (particularly if your diet is rich in fat), your medical history (such as diabetes), or regular use of medications, such as statins. Whether or not you need to stop taking any of these medications for the test depends on your physician's instructions.

Test Procedures

A healthcare professional will extract a blood sample from a vein, usually in your arm, using a tiny needle. Once the needle is placed, a little sample of blood will be drawn into a test tube. You may experience a slight stinging sensation when the needle is inserted or removed.

Normal and Abnormal Values

The test results are reported in milligrams per deciliter (mg/dL). The normal value of Apo B examination varies in men and women. These are the reference ranges for Apo B tests:

• The optimal range for a man ranges from 66–133 mg/dL
• The optimal range for a woman ranges from 60–117 mg/dL

The reference value could slightly vary in different laboratories. Normal apo B levels in individuals are below 100 mg/dL. Elevated levels indicate you have an increased susceptibility to develop cardiovascular disease in the future.

Results and Suggestions (Follow-Up Tests)

High levels of apo B are linked to an increased risk of developing cardiovascular disease and also directly related to elevated LDL and non-HDL cholesterol levels. The increase in cholesterol levels can occur as a result of a diet rich in fat and/or a reduced ability of the body to remove LDL from the bloodstream.

Abnormality in apo B levels might be associated with other factors. A number of the factors listed below have the potential to increase or decrease apo B levels.

Low levels of apo B may be observed in: 

• Individuals who are taking certain medications, including:
• Estrogen
• Statin
• Niacin, also known as vitamin B3
• Thyroxine
• Hyperthyroidism (a medical condition characterized by an overactive thyroid gland)
• Malnutrition
• Reye syndrome
• Weight loss
• Severe illness
• Liver cirrhosis 
• Surgical procedure

Elevated levels of apo B may be observed in:

• Individuals who are taking certain medications, including:
• Progestins (synthetic versions of progesterone)
• Diuretics
• Beta-blockers
• Androgens
• Diabetes 
• Nephrotic syndrome (a type of kidney disorder)
• Hypothyroidism (a medical disorder characterized by insufficient production of thyroid hormone)
• In pregnancy, there is a temporary elevation in apo B levels

Consult To The Right Doctor

The apo B test is not commonly requested. Experts are still in the process of determining the optimal uses for the apo B as one of the coming-up markers for cardiac risk. In certain situations, they provide extra information, although their purpose is not to substitute for the lipid tests that are currently commonly accessible.

For the best explanation of your test results, consult your physician or internist. The process of interpreting the test requires careful consideration of both the test results and one's overall health, risk factors, and symptoms.

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