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Results and clinical patterns
8% of people have an increased level of liver function tests after a routine evaluation. Some of them only experience a transient increase and do not have any symptoms at all. These transient elevations resolve after 3 weeks in 30% of cases. Thus, not every elevation of liver function test is the same as severe liver disease, and doctors should be able to differentiate when this is the case. Using liver function test patterns can be very useful to know when to worry and what liver disease is causing the problem.
These are the most important laboratory tests and their usual normal range values:
- ALT: Up to 45 IU/L
- AST: Up to 35 IU/L
- GGT: Up to 30 IU/L
- Alkaline phosphatase: 30 to 120 IU/L
- Bilirubin: 2-17 mcmole/L
- Albumin: 40-60 grams/L
- Prothrombin time: 10.9 – 12.5 seconds
When there’s an alteration in these values, we can see two main patterns: a hepatocellular pattern with a predominance of elevated aminotransferases and a cholestatic pattern with a predominance of bilirubin, alkaline phosphatase, and GGT.
- Hepatocellular pattern: In these cases, doctors should evaluate which aminotransferase is more elevated. When ALT is more elevated, we should think of viral hepatitis, fatty liver disease, or autoimmune hepatitis. It is also found in celiac disease, acute Budd-Chiari syndrome, and other conditions. When AST is more elevated, it is usually due to alcohol-related liver damage and cirrhosis. AST is also increased in myopathies in hemolysis, thyroid disease, and other non-hepatic conditions.
- Cholestatic pattern: In a cholestatic pattern, bilirubin, alkaline phosphatase, and GGT are more elevated than aminotransferases. This alteration can be caused by a bile duct obstruction, cholestasis, primary biliary cirrhosis, medication-induced cholestasis, and other liver conditions. Outside of the liver, alkaline phosphatase may also be increased in pregnancy, bone diseases, acute renal failure, and other conditions.
