Cholesterol test
Alternative names:
total cholesterol
How the test is performed:
Adult or child:
Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a tourniquet (an elastic band) or blood pressure cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the tourniquet to distend (fill 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 tourniquet 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.
Infant or young child:
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. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.
How to prepare for the test:
Fast for 8 to 12 hours before the test.
The health care provider may advise you to discontinue drugs that can affect the test (see "Special considerations").
Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:
How the test will feel:
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the test is performed:
This test is often performed to evaluate risks for heart disease.
Cholesterol is an important normal body constituent, used in the structure of cell membranes, synthesis of bile acids, and synthesis of steroid hormones. Since cholesterol is water insoluble, most serum (that is, noncellular) cholesterol is carried by lipoproteins (chylomicrons, VLDL, LDL, and HDL). The term "LDL" usually means LDL-cholesterol and "HDL" means HDL-cholesterol. Also, the term "cholesterol" usually means total cholesterol (VLDL + LDL + HDL). Chylomicrons are lipoproteins that are present shortly after a meal but disappear within about 2 hours in "normal" individuals.
Excess cholesterol in the blood has been correlated with cardiovascular disease. LDL is sometimes referred to as "bad" cholesterol, because elevated levels of LDL correlate most directly with coronary heart disease. HDL is sometimes referred to as "good" cholesterol since high levels of HDL are a negative risk factor for coronary heart disease. This is because one of the main functions of HDL is to take excess cholesterol to the liver for excretion in the bile. Actually, the best cholesterol-related parameter to measure as a risk factor for coronary heart disease is probably the LDL/HDL ratio.
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