ALT

Alternative names 
SGPT; Serum glutamate pyruvate transaminase; Alanine transaminase

Definition
A test that measures the amount of ALT in serum.

How the test is performed
Adult or child:
Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a tourniquet (an elastic band) or blood pressure cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the tourniquet to distend (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 tourniquet 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 cleansed 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. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.

How to prepare for the test
Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child’s age, interests, previous experiences, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child’s age:

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
This test is used to determine if a patient has liver damage. ALT is an enzyme involved in the metabolism of the amino acid alanine. ALT is in a number of tissues but is in highest concentrations in the liver. Injury to the liver results in release of the enzyme into the blood.

Normal Values

Normal range can vary according to a number of factors, including age and gender. Consult your physician or lab for interpretation.

What abnormal results mean

Greater-than-normal levels may indicate:

     
  • hepatitis (viral, autoimmune)  
  • use of hepatotoxic drugs  
  • hepatic (liver) ischemia (blood deficiency)  
  • Cirrhosis  
  • hepatic tumor

What the risks are

     
  • excessive bleeding  
  • fainting or feeling light-headed  
  • hematoma (blood accumulating under the skin)  
  • infection (a slight risk any time the skin is broken)  
  • multiple punctures to locate veins

Special considerations

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Johns Hopkins patient information

Last revised: December 5, 2012
by Potos A. Aagen, M.D.

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