Controlling your cholesterol is important. It helps reduce your risk of cardiovascular disease (CVD).
Low-density lipoprotein (LDL) is often referred to as “bad” cholesterol. It is the type of cholesterol associated with heart disease. However, the association is not simple. Although high levels of LDL are common in people with heart disease, more than half of people with CVD have normal levels of LDL cholesterol (Johns Hopkins).
Common LDL tests measure the total amount of cholesterol in your blood. However, this may not be as predictive of CVD as a measurement of the number of LDL particles. People with more, smaller particles have higher CVD risk than those with fewer, larger particles. The number of particles can be determined with an apolipoprotein B 100 (apo B) test.
Apo B is a protein found on the surface of LDL particles. Each LDL particle only has one copy of apo B. Therefore, a measurement of apo B tells how many particles there are in the blood.
The apo B test may be ordered if you have high triglyceride levels. Triglycerides are another type of cholesterol that are a major risk factor for CVD. High triglyceride levels may interfere with traditional LDL tests.
The Apo B test may also be ordered by your doctor if you have a family history of CVD or high cholesterol (hyperlipidemia).
Finally, this test may be used to monitor treatment for hyperlipdemia. Apo B levels should return to normal if treatment is working. If they remain elevated, a different treatment may be needed.
The apo B test is performed on a blood sample. This sample is generally taken by a nurse or lab technician. A needle will be used to draw blood from a vein in your hand or arm. The blood will be collected in a tube and sent to a lab for analysis. Once the results are reported by the lab your doctor will explain what they mean.
No preparation is required for this test. However, it is sometimes performed along with other tests that require fasting.
The only risks of this test are those associated with having a blood sample 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 or lightheadedness
- accumulation of blood under the skin, known as a hematoma
- development of infection at the puncture site
Specific results for will vary depending on the normal ranges for the particular lab analyzing the specimen.. Generally, normal levels of apo B are between 40 and 125 milligrams per deciliter (mg/dL).
High apo B levels can be caused by a number of health issues. These include:
- familial combined hyperlipidemia
- hypothyroidism (underactive thyroid gland)
- kidney disease (nephrotic syndrome with protein loss and elevated blood lipids)
- the use of certain drugs, such as diuretics, androgens, or beta blockers
Low levels of apo B in the body may also be problematic. They could indicate:
- hyperthyroidism (overactive thyroid gland)
- Reye syndrome, a rare degenerative brain condition
- cirrhosis(scarring) of the liver
- apolipoprotein B deficiency (Bassen-Kornzweig syndrome)