AST
Alternative names:
aspartate aminotransferase; serum glutamic-oxaloacetic transaminase; SGOT
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:
Fast for at least 4 hours before the test.
The health care provider may instruct you to discontinue drugs that may affect the test (for example, antihypertensives, cholinergic agents, coumarin-type anticoagulants, digitalis, erythromycin, isoniazid, methyldopa, oral contraceptives, opiates, and salicylates).
Spurious increases in AST may occur in pregnancy and after exercise.
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 experience, 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:
AST is in high concentration in heart muscle, liver cells, skeletal muscle cells, and to a lesser degree, in other tissues. Although elevated serum AST is not specific for liver disease, it is used primarily to diagnose and monitor the course of liver disease (in combination with other enzymes such as ALT, LDH, and ALP). It has also been used to monitor patients with heart attacks, but it is much less specific than CPK isoenzyme and LDH isoenzyme for this purpose.
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