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Blood test
Blood test

HDL

Definition:
This is a test that measures the amount of high-density lipoprotein (HDL) cholesterol in serum.



Alternative Names:
High-density lipoprotein



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.



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 experiences, 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 used in an evaluation of coronary risk factors.



Lipoproteins are proteins in the blood that transport cholesterol, triglycerides, and other lipids to various tissues. The main function of HDL appears to be carrying excess cholesterol (and probably other phospholipids and proteins) to the liver for "re-packaging" or excretion in the bile.



Higher levels of HDL seem to be protective against coronary artery disease, thus HDL is sometimes referred to as "good" cholesterol. The laboratory test for HDL actually measures the cholesterol part of HDL, not the actual concentration of HDL in the blood.

This is also true of the tests for low density lipoprotein (LDL) and very low density lipoprotein (VLDL). The total cholesterol level is the sum of LDL, HDL, and VLDL cholesterol.





Normal Values:

Women tend to have better HDL cholesterol than men. In general, an increased risk for heart disease, including heart attack, occurs when the HDL level is less than 40mg/dL. More specifically, men are at particular risk if their HDL is below 37 mg/dL and women if their HDL is below 47 mg/dL.

An HDL 60mg/dL or above helps protect against heart disease.





What abnormal results mean:
Low HDL levels may indicate an increased risk of atherosclerotic heart disease.



Additional conditions under which the test may be performed:



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:
HDL will usually be performed as part of an overall lipid profile, wherein LDL, and triglycerides will also be measured. The combination of all these different types of fats can help determine cardiovascular event risk (i.e., heart attack, stroke, and peripheral vascular disease).



Review Date: 8/23/2002

Reviewed By: A.D.A.M. editorial (8/23/02). Previous review: Jeffrey Heit, M.D., Department of Medicine, University of Pennsylvania Health System, Philadelphia, PA. Review provided by VeriMed Healthcare Network (10/27/01).

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