Definition This test measures the level of low-density lipoprotein (LDL) in the blood.
High levels of LDL are often associated with development of heart disease. LDL is linked to fatty deposits on the wall of the arteries; a condition called arteriosclerosis, and is known as the "bad" cholesterol.
Who is a candidate for the test? The LDL test is usually performed to evaluate risk of heart attack or vascular disease.
How is the test performed? The first step in measuring LDL cholesterol is to take a blood sample. Blood is usually drawn from a vein in the forearm or the hand. To do this, the skin over the vein is cleaned with an antiseptic. Next, a strong rubber tube, or tourniquet, is wrapped around the upper arm. This enlarges the veins in the lower arm by restricting blood flow through them. A very thin needle is gently inserted into a vein and the tourniquet is removed. Blood flows from the vein through the needle and is collected into a syringe or vial. The sample is sent to the laboratory to be analysed for LDL cholesterol. After the needle is withdrawn, the puncture site is covered for a short time to prevent bleeding.
What is involved in preparation for the test? Individuals having this test should request specific instructions from their doctors.
What do the test results mean? Normal levels of LDL in the blood range from 1.5 mmols/L to 4.6 mmols/L (millimoles per litre). The recommended level of LDL cholesterol is less than 3.4 mmols/L.
Abnormally high levels of LDL may mean:
increased risk of atherosclerotic heart disease, or narrowing of the arteries due to fatty deposits called plaques
high cholesterol levels due to heredity, called familial hyperlipoproteinaemia
Abnormally low levels of LDL may indicate:
malabsorption of nutrients from the intestinal tract
Author: David T. Moran, MD Reviewer: eknowhow Medical Review Panel Editor: Dr John Hearne Last Updated: 23/10/2004 Contributors Potential conflict of interest information for reviewers available on request
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