Hepatitis:Common Blood Tests/Liver Function

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Liver Function Tests (or Liver Enzymes) - Includes blood tests that assess the general health of the liver. When elevated above normal values, the ALT (alanine aminotransferase) and AST (aspartate aminotransferase) tests indicate liver damage. They are enzymes located in liver cells that can leak out into the bloodstream when liver cells are injured.

ALT (alanine aminotransferase)—ALT is an enzyme that is normally found in the liver cells and in the blood. When liver cells become damaged, they leak into the bloodstream, causing levels of liver enzymes to be raised. An increase in ALT levels can indicate acute liver damage. However, a single ALT test cannot usually reveal the severity of liver damage. Many people with chronic hepatitis C have normal ALT levels, so this test is not considered a completely accurate marker of disease progression.

AST is found in other organs besides the liver. High AST levels in the bloodstream can be a sign of liver trouble. AST testing measures the level of AST in a person's bloodstream at a given time. Like ALT levels, AST levels in people with HCV often vary over time and can't be used to forecast disease progression or specifically measure liver damage.

Bilirubin
When red blood cells complete their lifecycle and break down naturally, they produce bilirubin, a yellow pigment that's passed on to the liver and excreted in the bile. Most of the time, the body produces as many red blood cells as it breaks down. However, if the red blood cells break down more rapidly or if liver function becomes impaired, bilirubin levels in the blood rise. In patients with hepatitis, bilirubin levels tend to fluctuate. A prolonged persistent rise in bilirubin for a patient with chronic hepatitis C usually indicates severe liver dysfunction.

Albumin
Albumin is a protein manufactured by the liver. A decrease in albumin may reflect a reduction in the liver's ability to synthesize this protein, and a significant sustained decrease in this protein may mean poor liver function. However, decreases in albumin levels may also occur for reasons not related to the liver. Your doctor will take this into account when interpreting test results.

Prothrombin time
This test measures blood clotting ability. When the liver is damaged, it may fail to produce enough blood clotting factors.
Complete blood count—A complete blood count analysis can be used to help detect liver scarring. If the liver becomes scarred, blood may back up into the spleen. This causes the spleen to enlarge and to trap blood elements, removing them from circulation and lowering blood counts.

Ferritin
Iron is stored in the liver in the form of ferritin. Increased levels of ferritin means a high level of iron is being stored. This could result from an increased iron intake in the diet (vitamin supplements, food cooked in iron pots, etc.), but it can also occur from a destruction of liver cells causing leakage of ferritin. More research is needed to understand the relationship between elevated ferritin and liver cancer.