Alternate Names: LDH4; LDH5; LDH3; Lactic dehydrogenase isoenzymes; Lactate dehydrogenase isoenzymes; LD1; LD3; LD4; LD2; LDH2; LDH1; LD5
How 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: 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 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 It Feels: 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.
Risks:
- excessive bleeding
- fainting or feeling lightheaded
- hematoma (blood accumulating under the skin)
- infection (a slight risk any time the skin is broken)
- multiple punctures to locate veins
Why Performed: This test is usually performed when LDH levels are elevated. Measurement of LDH isoenzymes is helpful to differentiate the source (location) of tissue damage.
The enzyme LDH is in many body tissues especially heart, liver, kidney, skeletal muscle, brain blood cells, and lungs. LDH catalyzes the interconversion of pyruvate and lactate.
LDH exists in 5 forms, called isoenzymes, which differ slightly in structure. LDH-1 is in highest concentrations in heart muscle and red blood cells. LDH-2 is highest 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.
Normal Values:
- LDH (total): 115 to 225 IU/L
- LDH-1: 17 to 27 %
- LDH-2: 27 to 37 %
- LDH-3: 18 to 25 %
- LDH-4: 3 to 8 %
- LDH-5: 0 to 5 %
Note: IU/L = international units per liter
Abnormal Results: Because LDH is in many tissues in the body, total LDH is not a good indicator of heart disease. Normally, the concentration of LDH-2 is higher than of LDH-1. However, after a heart attack, the concentration of LDH-1 is generally higher than that of LDH-2 (this is called a "flipped" LDH pattern). The serum LDH level rises within 24 to 72 hours after a heart attack, peaks in 3 to 4 days, and returns to normal in about 14 days.
Greater-than-normal LDH isoenzyme levels may be seen in:
Additional conditions under which the test may be performed:
Cost:
Special Considerations: Drugs that can increase LDH measurements include anesthetics, aspirin, clofibrate, fluorides, mithramycin, narcotics and procainamide.
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 from others.
