From the Guidelines
Liver function tests (LFTs) that assess liver health include alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP), bilirubin, albumin, and prothrombin time, which provide a comprehensive picture of liver health. These tests are valuable because the liver performs numerous vital functions including detoxification, protein synthesis, and metabolic processes, and abnormalities in these tests can indicate various liver conditions such as hepatitis, cirrhosis, or medication-induced liver injury 1. The main tests can be categorized into:
- Liver cell damage: ALT and AST
- Bile duct function: ALP
- Waste product processing: bilirubin
- Synthetic function: albumin and prothrombin time
For accurate interpretation, these tests should be considered collectively rather than in isolation, as patterns of abnormalities often provide more diagnostic information than individual test results 1. It is also important to note that the severity of abnormal aminotransferase can be classified as mild, moderate, or severe, and that moderate and severe elevations are discussed collectively due to significant clinical overlap 1.
In patients with symptoms or signs of cirrhosis, portal hypertension, or liver failure, liver blood tests, including INR, are important to monitor their function 1. However, the most recent and highest quality study 1 provides the most relevant information for assessing liver function.
The liver function tests are essential for monitoring liver health, and abnormalities in these tests can indicate various liver conditions, and the combination of ALT, AST, ALP, bilirubin, albumin, and prothrombin time provides a comprehensive picture of liver health 1.
From the Research
Laboratory Tests for Liver Function
The following laboratory tests are used to assess liver function:
- Serum aminotransferases (AST, ALT) 2, 3, 4, 5
- Alkaline phosphatase 2, 3, 4, 5
- Bilirubin levels (total and direct) 2, 3, 4, 6
- Albumin levels 2, 3, 4
- Prothrombin time 2, 3, 4
- Gamma glutamyl transferase (GGT) 3, 6
- Protein electrophoresis 4
- Viral hepatitis serologies 5
- Markers of proliferation (e.g. α-fetoprotein) 5
Interpretation of Test Results
The interpretation of these test results can help diagnose specific liver diseases, such as hepatitis, biliary obstructions, or infiltrative liver disease 2, 3. The pattern of liver test abnormalities can suggest the underlying cause of liver disease 2, 3. For example, cytolytic elevation in serum aminotransferases may indicate pharmacological toxicity, viral hepatitis, alcoholic or non-alcoholic fatty liver disease, or hemochromatosis 3.
Limitations and Future Directions
While these laboratory tests are useful in assessing liver function, they have limitations. For example, ALT and AST have poor prognostic utility in acute liver injury and liver failure 5. New biomarkers of liver injury are being developed, which may complement or replace existing tests in the future 5.