Abnormal Liver Function Test Results - Quick Reference

This is a Quick Reference article. See also the main article Assessing a patient with an abnormal liver function test result Assessing a Patient with an Abnormal Liver Function Test Result.

Liver enzymes

ALT (alanine aminotransferase) is principally a liver cell enzyme, and only small amounts are encountered elsewhere. ALT is the first-line screening test for a liver disease.
AST (aspartate aminotransferase) is less specific. In addition to liver cells, it may be released into blood stream from muscles, red blood cells, kidneys and brain.
GT (glutamyl transferase) is a sensitive but non-specific marker of liver damage. Increased concentration may be due to hepatocellular damage, cholestasis or, for example, drug-induced enzyme induction.
Alkaline phosphatase originates from biliary ducts or bones.
Slight increase = 2-5 × the upper limit of reference range; encountered in about 10% of population.

Fatty liver
- Alcoholic: AST higher than ALT (ratio > 1). Even moderate alcohol consumption can increase GT.
- Non-alcoholic (NAFLD), most commonly associated with metabolic syndrome: ALT higher than AST
- Associated with obesity with increasing frequency.
Chronic viral hepatitis Viral Hepatitis
- ALT is normal to slightly increased in hepatitis B.
- Usually between 80 and 200 IU/l in hepatitis C.
Liver cirrhosis
- In asymptomatic cirrhosis, ALT and AST are only slightly increased. If clinical picture is suggestive of liver cirrhosis, check other liver function tests: albumin, prealbumin, bilirubin and INR.
Drug-induced and other toxic injury
- If suspected, stop the drug immediately and check levels again after a few days to weeks.
Autoimmune liver disease
- Primary biliary cirrhosis Primary Biliary Cholangitis, primary sclerosing cholangitis Primary Sclerosing Cholangitis: alkaline phosphatase increases the most, AST and ALT may remain normal.
Rare causes
- Storage diseases (iron, amyloidosis), vasculitis, Wilson's disease

Incidental finding
- History (alcohol, medication, illegal substances, blood transfusions, natural remedies)
- If asymptomatic, re-check after 2-3 months.
- Stop the drug if drug reaction is suspected, re-check within about one week.
Excessive alcohol consumption
- Abstinence for 1 month then re-check
Diagnostics of viral hepatitis: see Viral hepatitis Viral Hepatitis
Upper abdominal ultrasonography
- Inadequate sensitivity and specificity in parenchymal disease
- Suitable for the investigation of focal changes and biliary tract disease.
Liver biopsy in specialist care, does not require hospitalisation. Assess bleeding risk (blood platelets, INR/thromboplastin).
Indications for liver biopsy
- Persistent (> 6 months) increase of liver function results for an unknown reason
- Verification of diagnosis in storage and autoimmune diseases
- Assessment of the severity of injury in liver cirrhosis or chronic viral hepatitis