LDH isoenzymes Health Article

Definition

LDH isoenzymes is a test to check how much lactate dehydrogenase (LDH) is in the blood.

Alternative Names

LD; Lactic (lactate) dehydrogenase isoenzymes

How the test is performed

Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. 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.

Next, 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.

Once the blood has been collected, the needle is removed, and 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. 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 anesthetics, aspirin, clofibrate, fluorides, mithramycin, narcotics, and procainamide.

How the test will feel

When the needle is inserted to draw blood, you may feel moderate pain, or only a prick or stinging sensation. 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 tissue damage.

LDH is found in many body tissues like 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.