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CHEM-20

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Definition:

Chem-20 is a group of 20 chemical tests performed on serum (the portion of blood without cells).

These tests include total cholesterol, total protein, and various electrolytes . Electrolytes in the body include sodium, potassium, chlorine, and many others.

The rest of the tests looks at chemicals that help the liver and kidney breakdown various substances.

Alternative Names:

SMA20; Sequential multi-channel analysis with computer-20; SMAC20; Metabolic panel 20

How the test is performed:

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a band is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the band to 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 band 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 cleaned 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. A bandage may be applied to the puncture site if there is any continued bleeding.

How to prepare for the test:

The patient should try not to eat overnight before the test.

How the test will feel:

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.

Why the test is performed:

Blood chemistry measures the levels of a number of chemical substances that are released from various tissues in the body. The amounts of these chemicals in the blood may reflect abnormalities in the tissues secreting them.

• Review Date: 3/22/2007
• Reviewed By: Benjamin W. Van Voorhees, MD, MPH, Assistant Professor of Medicine, Pediatrics and Psychiatry, The University of Chicago, Chicago, IL. Review provided by VeriMed Healthcare Network.

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