CHEM-20

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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 are ionized salts in blood or tissue fluids (ions are atoms or molecules that carry an electrical charge). Electrolytes in the body include sodium, potassium, chlorine, and many others.

The rest of the tests focus primarily on chemicals related to the body's metabolism and the breakdown of various substances. These are tests that evaluate the function of the liver and kidneys.

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

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.

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

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.

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: 06/13/2005
Reviewed By: Nader Najafian, M.D., Associate Physician, Renal Division, Brigham & Women's Hospital, Instructor of Medicine, Harvard Medical School, Boston, MA. Review provided by VeriMed Healthcare Network.