Apolipoprotein B100Definition: Apolipoprotein B100 measures the amount of apolipoprotein B100 (apoB100) in the blood. Lipoproteins are large complexes of molecules that transport lipids (primarily triglycerides and cholesterols) through the blood. Apolipoproteins are proteins on the surface of the lipoprotein complex that bind to specific enzymes or transport proteins on the cell membranes -- this directs the lipoprotein to the proper site of metabolism. ApoB100 is in an intermediate form of lipoprotein (IDL) and an low density lipoprotein (LDL).
Alternative Names: ApoB100; Apoprotein B100
How the test is performed: Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic. An elastic band is placed around the upper arm to apply pressure and cause the vein to swell with blood. A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding. In infants or young children: The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. A bandage may be applied to the puncture site if there is any bleeding.
How to prepare for the test: Fasting for 4 - 6 hours may be recommended.
How the test will feel: When the needle is inserted to draw blood, you may feel moderate pain, or only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the test is performed: Most often, this test is performed to help determine the cause of hyperlipidemia (elevated blood lipid levels). ApoB100 is a form of apoB that occurs in LDL and IDL but not in chylomicrons (large lipoprotein particles that contain apoB48 and other apolipoproteins).
Normal Values: The normal range is 40 to 125 mg/dL. Normal value ranges may vary slightly among different laboratories.
What abnormal results mean: Elevated levels of apoB occur in familial combined hyperlipidemia and acquired hyperlipidemia (elevated blood lipid levels). ApoB100 measurements can help to determine the specific type or cause of hyperlipidemia. Other disorders that may be associated with elevated apoB levels include angina pectoris and heart attack.
What the risks are: - Excessive bleeding
- Fainting or feeling light-headed
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
- Multiple punctures to locate veins
Special considerations: Apolipoprotein levels can be measured directly, unlike HDL and LDL measurements, which are indirect. This test may give a much more accurate picture of your health, including your risk for heart disease. Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than others.
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