What Is the Apolipoprotein B100 Test?

Apolipoprotein B100 (apoB100) is the primary protein in low-density lipoprotein (LDL) cholesterol. The apoB100 test measures the amount of this type of cholesterol in the blood. LDL is often referred to as “bad” cholesterol because high levels of it can damage the heart and blood vessels. Each LDL particle has one copy of apoB100, so a measurement of apoB100 levels shows how many LDL particles there are in the blood.

High levels of apoB100 indicate high cholesterol, which is a known risk factor for heart disease. Your doctor may order an apoB100 test along with other lipid tests if you have a family history of heart disease or if you have high levels of fat in your blood. These tests can help determine your risk for heart disease. The apoB100 test may not always be predictive of heart disease. High levels of LDL are common in people with heart disease, but many people with the condition have normal levels of LDL cholesterol.

Your doctor may order an apoB100 test if you have a family history of heart disease or high cholesterol, or hyperlipidemia. They may also order the test if you have high levels of fats, such as cholesterol and triglycerides, in your blood. Elevated levels of fat can increase your risk for serious heart problems, including heart disease and atherosclerosis.

Your doctor may also order the apoB100 test if you’re currently being treated for hyperlipidemia, or high cholesterol in the blood. The test results can enable your doctor to determine how well treatment is working to lower cholesterol levels in your blood. ApoB100 levels should return to normal if treatment is working. If they remain elevated, you may need a different type of treatment.

Your doctor will give you specific instructions to follow. In most cases, however, you won’t be allowed to consume anything except water for several hours before the test. Make sure to ask your doctor how long you need to fast. It’s also important to notify them about any prescription drugs, over-the-counter medications, or supplements you may be taking. Your doctor might ask you to stop taking certain medicines that may interfere with the accuracy of the test.

The apoB100 test involves taking a small sample of blood from a vein in your hand or arm. The test involves the following steps:

  1. A healthcare provider will tie a tight band known as a tourniquet around your arm. This will make your veins easier to see.
  2. They’ll clean the desired area with an antiseptic
  3. Then, they’ll insert the needle. You may feel a slight prick or stinging sensation when the needle goes in. They’ll collect your blood in a tube or vial attached to the end of the needle.
  4. Once enough blood has been collected, they’ll remove the needle and apply pressure to the puncture site for a few seconds.
  5. They’ll then put a bandage or gauze over the area where the blood was drawn.
  6. After the test, they’ll send your blood sample to a laboratory for testing.

Your doctor will follow up with you to explain the results.

The only risks of an apoB100 test are those associated with having blood drawn. The most common side effect is mild pain at the puncture site during or after the test. Other possible risks from a blood draw include:

  • difficulty obtaining a sample, resulting in multiple needle sticks
  • excessive bleeding at the puncture site
  • fainting
  • dizziness
  • lightheadedness
  • accumulation of blood under the skin, which is known as a hematoma
  • an infection at the puncture site

Specific results for will vary depending on the normal ranges defined by the particular laboratory that analyzed the blood sample. Generally, normal levels of apoB100 are between 40 and 125 milligrams per deciliter (mg/dL).

High apoB100 levels can be associated with certain health issues, including:

  • familial combined hyperlipidemia, which is an inherited disorder that causes high cholesterol and triglyceride levels
  • diabetes, which is a disease in which the body either doesn’t produce enough insulin or is resistant to it, leading to high blood sugar
  • hypothyroidism, which is a disorder in which the thyroid gland fails to produce a sufficient amount of hormones
  • kidney disease
  • the use of certain drugs, such as diuretics, androgens, or beta-blockers

Low apoB100 levels may also be problematic. They could indicate:

  • hyperthyroidism, which is a disorder in which the thyroid gland produces an excessive amount of hormones
  • Reye’s syndrome, which is a rare yet serious condition that causes sudden swelling in the brain and liver
  • abetalipoproteinemia, which is a condition that prevents the body from properly absorbing dietary fats
  • cirrhosis, or severe scarring of the liver
  • malnutrition

Regardless of your test results, it’s critical to speak with your doctor about what they may mean for you specifically.