LDH isoenzymes is a test to check how much of the different types of lactate dehydrogenase (LDH) are in the blood.
LD; Lactic (lactate) dehydrogenase isoenzymes
How the Test is Performed
The procedure is done in the following way:
- The site is cleaned with germ-killing medicine (antiseptic).
- The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.
- The health care provider gently inserts a needle into the vein.
- The blood collects into an airtight vial or tube attached to the needle.
- The elastic band is removed from your arm.
- The needle is removed.
- The puncture site is covered to stop any bleeding.
In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. Afterward, a bandage may be placed over the area if there is any bleeding.
How to Prepare for the Test
The health care provider may tell you to stop taking certain medicines before the test.
Drugs that can increase LDH measurements include:
How the Test will Feel
When the needle is inserted to draw blood, you may feel slight pain or only a prick or stinging. Afterward, there may be some throbbing.
Why the Test is Performed
This test is usually done when your doctor thinks you might have high LDH levels. Measurement of LDH isoenzymes helps determine the location of any tissue damage.
LDH is found in many body tissues such as the heart, liver, kidney, skeletal muscle, brain, blood cells, and lungs.
LDH exists in 5 forms, 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 can be measured in the blood.
What Abnormal Results Mean
LDH levels that are higher than normal may suggest:
- Heart attack (though this test is no longer used routinely to diagnose a heart attack as there are more accurate methods)
- Hemolytic anemia
- Infectious mononucleosis
- Intestinal ischemia (blood deficiency) and infarction (tissue death)
- Ischemic cardiomyopathy
- Liver disease such as hepatitis
- Lung tissue death
- Muscle injury
- Muscular dystrophy
- Lung tissue death
Veins and arteries vary in size from one patient to another and from one side of the body to the other. Drawing blood from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
- Excessive bleeding
- Fainting or feeling light-headed
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
Pincus MR, Abraham NZ Jr, Carty RP, et al. Clinical enzymology. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 20.
Chinnery PF. Muscle diseases. In: Goldman L, Schafer AI, eds. In: Goldman’s Cecil Medicine. 24th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 429.