What It Is

The hepatic function panel, also known as liver function tests, is a group of seven tests used to evaluate the liver for injury, infection, or inflammation.

The liver plays important roles: It stores energy from food, makes proteins, and helps remove toxins. The liver also makes bile, a fluid that helps in digestion.

Why It's Done

Liver function tests help doctors find out whether the liver has been damaged. If your child is experiencing symptoms of liver disease — including jaundice (yellowish skin or eyes), dark urine, nausea, vomiting, or abdominal swelling — these tests may be ordered. They may also be done to help diagnose viral infections (such as hepatitis or mononucleosis) or to monitor medications that can cause liver-related side effects.

The hepatic function panel evaluates:

• Alanine aminotransferase (ALT). This enzyme, found in the liver, plays a role in metabolism, the process that converts food into energy. If the liver is injured, ALT is released into the bloodstream. Its levels are especially high with acute hepatitis.
• Alkaline phosphatase (ALP). This enzyme is found in the liver, bones, intestines, kidneys, and other organs. Kids and teens normally have higher levels of ALP than adults, even when they're healthy, due to bone growth. But ALP levels can also increase when kids have viral infections, liver diseases, or blocked bile ducts.
• Aspartate aminotransferase (AST). This enzyme, which plays a role in processing proteins, is found in the liver, heart, muscles, and kidneys. When the liver is injured or inflamed, levels of AST in the blood usually rise.
• Total bilirubin and direct bilirubin. Bilirubin is a byproduct of the normal breakdown of red blood cells. It usually passes through the liver and is excreted from the body. But if that doesn't happen due to a liver disease, bilirubin levels in the blood can rise and the skin can take on the yellow discoloration known as jaundice. Tests for bilirubin may be total (measuring the level of all of the bilirubin in the blood) or direct (measuring only bilirubin that has been processed by the liver and attached to other chemicals).
• Albumin and total protein. Protein is needed to build and maintain muscles, bones, blood, and organ tissue. Sometimes when there's a problem with the liver, it can't make proteins as well, so protein levels decrease. Liver function tests measure albumin specifically (the major blood protein produced by the liver), as well as the total amount of all proteins in the blood.

Preparation

Although the hepatic function panel can be done without any preparation, it's more accurate when performed after fasting. Your child may be asked to stop eating and drinking for 10 to 12 hours before this blood test. You should also tell your doctor about any medications your child is taking because certain drugs might alter the test results.

On the day of the test, having your child wear a short-sleeve shirt can make things easier for the technician who will be drawing the blood.