Lifespan's A - Z Health Information Library

This is a blood test that measures the amount of 5-N'Tase.

Blood is drawn from a vein on the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and an elastic 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.

For an 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.

Your health care provider will instruct you, if necessary, to discontinue drugs that may interfere with the test. These include drugs that can damage the liver, such as Tylenol (acetaminophen), methyldopa, nitrofurantoin, isoniazid, and halothane.

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.

Serum 5'-N'Tase is measured as an indicator of liver damage resulting primarily from interference with the secretion of bile. Serum 5'-N'Tase is not as sensitive as some other enzymes (for example, ALP, AST, and ALT) to liver damage, but it is a more liver-specific enzyme. It is used mostly to differentiate elevated enzymes due to liver damage from elevated enzymes due to skeletal muscle damage.

The normal value is 2 to 17 U/L.

Note: U/L = units per liter

Greater than normal levels of 5'-N'Tase may indicate:

• cholestasis (congestion of the biliary system, such as gall stones)
• liver ischemia (inadequate blood flow in the liver)
• liver necrosis (destruction of liver cells)
• liver tumor
• hepatitis
• use of a hepatotoxic (liver-damaging) drug

The risks associated with having blood drawn are:

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

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.