Apolipoprotein B Test

Apolipoprotein B profile test measures the condition of high cholesterol and cardiovascular diseases. It also helps diagnose a very rare inherited deficiency of apolipoprotein B. Apo B is a structural apolipoprotein of LDL particles that facilitates their transportation to the peripheral tissues. It is also the main protein constituent of lipoproteins like very low-density lipoprotein (VLDL) and low-density lipoprotein (LDL). LDL is actually bad cholesterol. Hence, the apolipoprotein B test measures the amount of Apo B in the bloodstream.

Most lipoproteins are triglyceride and cholesterol-rich, which carry the lipids through the body for the usage of the cell. Lipids are not soluble with water and thus, they have to combine with apolipoproteins to travel in the bloodstream. Apolipoproteins are also good at providing structural integrity to the lipoproteins by protecting them from the water-repellent hydrophobic lipids at their centre.

Lipoprotein particles known as chylomicrons carry the dietary lipids from the digestive tract through the bloodstream to the tissue, mainly the liver. The liver then repackages these dietary lipids and combines them with Apo B-100 to form triglyceride-rich VLDL. This combination is like a cab full of passengers with Apo B-100 as the cab driver. In the bloodstream, the cab moves from one place to another while releasing one passenger at a time.

Lipoprotein lipase is an enzyme responsible for removing triglycerides from VLDL to produce intermediate-density lipoproteins and LDL. Each VLDL particle consists of one molecule of Apo B. This is retained as VLDL, which loses the triglycerides and shrinks to become a cholesterol-rich LDL. Apo B is recognised by the receptors found on the surface of the body's cells. These receptors have the responsibility of promoting the uptake of cholesterol into the cells.

The cholesterol that Apo B-100 and LDL transports are important for cell membrane integrity, steroid production and sex hormone production. However, if the amount of LDL exceeds in the body, it can lead to fatty deposits in artery walls with hardening and scarring of the blood vessels. The fatty depositions narrow the blood vessels and this increases the chances of a heart attack.

Apo B-100 levels are almost directly proportional to LDL-C levels. However, medical experts feel that the results of apolipoprotein B test are a better indicator of the risk of cardiovascular disease compared to LDL-C.

Apolipoprotein B test is usually included in the complete lipid profile test. The doctor will usually ask you to take the test if you have a family history of heart diseases and high cholesterol with triglycerides. It also helps in understanding the cause of abnormal lipid levels when someone has high triglyceride levels.

Apolipoprotein B test is prescribed to monitor the effectiveness of the lipid treatment as well. In some cases, the Apo B test helps diagnose a genetic problem that causes over or underproduction of Apo B.

High cholesterol and triglycerides are common health conditions in India. People from urban and rural areas both have this problem because of hectic and unhealthy lifestyles. The urban population has developed this issue because of stress and poor sleep cycle as well. Poor nutrition also adds to these problems.

High Cholesterol, Cardiovascular disease

The Apolipoprotein B1 test measures the amount of Apo B-100 in the blood.

For people with such symptoms, amongst other tests, the Apolipoprotein B1 test is prescribed by the consulting physician.

Some disease conditions for which an Apolipoprotein B1 test can be prescribed are:

• Nephrotic syndrome, which is a kidney disease
• Severe illnesses
• Diabetes
• Hypothyroidism
• Surgery
• Uses of drugs like beta-blockers, androgens, progestins and diuretics
• Pregnancy
• Uses of drugs like lovastatin, estrogen, simvastatin, thyroxine and niacin

Decreased Apo B levels affect lipoprotein production and affect synthesis and packaging in the liver. Also, an increased ratio of Apo B to Apo A-I indicates a higher risk of developing cardiovascular disease.

Following a diagnosis, once a physician or endocrinologist initiates the treatment for Apo B-100, the Apolipoprotein B profile test may be prescribed every 3 months to monitor and regulate the dosage. The results of the Apolipoprotein B test may help your doctor continue the same treatment or modify the dosage.

The Apolipoprotein B test is applicable for males and females, both adults and children.

A random Apolipoprotein B profile test helps diagnose cardiovascular diseases, high cholesterol and deficiency of Apo B-100. If the result of the Apolipoprotein B profile test confirms a diagnosis, appropriate medication should be taken. The test has to be repeated every month or three months to monitor the effectiveness of the medication.

The Apolipoprotein B1 test can be taken annually with the lipid profile test if the results are normal.

Before the Test

It is essential to refrain from eating or drinking for a duration of A to B hours before the Apolipoprotein test. This fasting is vital for ensuring the accuracy of the results. Consequently, it is advisable to consult with a healthcare professional prior to any test to ascertain if there are any particular guidelines to be followed.

During the Test

A blood sample will  be drawn from a vein in your arm. The procedure includes:

• Cleansing the area where the needle will be inserted with an antiseptic solution.
• Applying a tourniquet around your arm to enhance the visibility of the veins.
• Inserting a sterile needle into the vein to draw the blood, which may result in slight discomfort and will take only a few seconds.
• Transferring the collected sample into a small container or test tube labelled with your test details.

After the Test

Once the blood sample is collected:

• A bandage will be placed over the site of the needle insertion to minimise any bleeding.
• It is common to experience mild soreness or lightheadedness, which should not be a cause for alarm. You may be instructed to rest for a brief period.
• Should you notice any bleeding, discomfort, or rashes at the site of the puncture, please reach out to your healthcare provider.

The Apolipoprotein B1 test measures the amount of Apo B-100 in your blood. It can also tell you whether you have a deficiency of Apo B-100 or not.

These values will help you evaluate the risk of having cardiovascular diseases. The result of the Apolipoprotein B1 test is not expressed as positive or negative. If the value is on the higher or lower side, it is an indicator of disorder in the body, especially related to the heart. The test is also prescribed if you have any family history of Apo B-100.

The normal range of Apo B-100 in adults should be less than 100 mg/dL. If you have more than 110 mg/dL of Apo B-100, you have a greater risk of developing cardiovascular diseases.

The normal values and reference ranges of the test may vary from lab to lab. Please refer to the ranges mentioned in the report and consult a doctor to understand the interpretation of lab reports.

High levels of Apo B correspond to high levels of LDL-C and the non-HDL-C is associated with an increased risk of cardiovascular diseases. Elevated levels are also because of a high-fat diet and decreased clearing of LDL from the blood.

If the results of Apolipoprotein B test are abnormal, then that can be because of genetic disorders. For example, if you have familial combined hyperlipidemia, it is because of an inherited disorder of high blood levels of cholesterol and triglycerides. Apolipoprotein B deficiency or Abetalipoproteinemia is also a very rare genetic condition that can cause abnormally low levels of Apo B.

Abnormal levels of Apo B can be because of:

• Diabetes
• Hypothyroidism
• Nephrotic Syndrome
• Hyperthyroidism
• Reye Syndrome
• Cirrhosis
• Cardiovascular diseases

If the Apolipoprotein B profile test results are abnormal, it warrants further investigation for underlying conditions. These underlying conditions can be related to the kidneys, liver, and heart.