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Ency. home > Test > L > LDH isoenzymes

LDH isoenzymes   

Overview | Risks | Results

Alternative names:

LD;  Lactic dehydrogenase isoenzymes; Lactate dehydrogenase isoenzymes

Definition:

This is a test that measures the amount of the isoenzymes (different forms) of lactate dehydrogenase (LDH) in serum.

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 cause 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

The health care provider may advise you to withhold drugs that may affect the test (see special considerations).

Infants and children:
The physical and psychological preparation involved in readying a child for any test or procedure depends on the 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 may feel moderate pain, while others may feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the Test is Performed

This test is usually performed when elevated LDH levels are suspected. Measurement of LDH isoenzymes is helpful in determining the location of the tissue damage.

The enzyme LDH is found in many body tissues like the heart, liver, kidney, skeletal muscle, brain, blood cells, and lungs. LDH is very important for metabolism.

LDH exists in 5 forms -- isoenzymes, which differ slightly in structure. LDH-1 is found primarily in heart muscle and red blood cells. LDH-2 is concentrated in white blood cells. LDH-3 is highest in the lung. LDH-4 is highest in the kidney, placenta, and pancreas. LDH-5 is highest in the liver and skeletal muscle. All of these isoenzymes can be measured in the blood.

Ency. home > Test > L > LDH isoenzymes

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