This test measures the blood levels of three forms of the enzyme creatine phosphokinase, which is also called CPK. These forms are known as isoenzymes. They are called CPK-BB, CPK-MB, and CPK-MM.
This blood test determines the amounts of each of these isoenzymes in the blood. These levels can help a doctor to diagnose certain illnesses and conditions.
Damage to the brain, lungs, heart, or muscle may cause the corresponding isoenzyme to leak into the bloodstream.
In order to measure the amount of CPK isoenzymes in the blood, a blood sample is taken from a vein on the forearm or hand. First, the skin over the vein is cleaned with an antiseptic. Next, a rubber tube called a tourniquet is tied around the upper arm. This enlarges the veins in the lower arm by restricting blood flow through them. A fine needle is gently inserted into a vein, and the tourniquet is removed. Blood flows from the vein through the needle and is collected in a syringe or vial for testing in the laboratory. After the needle is withdrawn, the puncture site is covered for a short time to prevent bleeding.
Normally, no preparation is required for this test.
If a disease process is taking place, the total amount of CPK will be high, and the individual isoenzyme increases are used to determine what part of the body is responsible for the increase in total CPK. For example, when a heart attack occurs, the total CPK becomes high because of an increase in the CPK-MB and CPK-MM isoenzymes. The normal total CPK level is roughly 25 to 175 units per liter. Normal values for each of the isoenzymes are as follows:
Abnormally high levels of CPK-BB may sometimes be seen in the following:
Abnormally high levels of CPK-MB may indicate the following:
Abnormally high levels of CPK-MM may indicate the following:
Author:David T. Moran, MD
Editor:Crist, Gayle P., MS, BA
Reviewer:Adam Brochert, MD