What tests are included in a hepatic (liver) function panel?

Components of a Hepatic Function Panel

A standard hepatic function panel should include bilirubin, albumin, ALT, ALP, and GGT, together with a full blood count if not already performed within the previous 12 months. 1

Core Components of a Hepatic Function Panel

The standard hepatic function panel consists of several key measurements that assess different aspects of liver function:

Liver Enzymes

• Alanine Aminotransferase (ALT): Most specific marker for liver damage 2
• Alkaline Phosphatase (ALP): Elevated in biliary tract involvement and cholestatic patterns of injury 1, 2
• Gamma-Glutamyl Transferase (GGT): Increases sensitivity for detecting liver disease, particularly alcohol-related and non-alcoholic fatty liver disease 1
• Aspartate Aminotransferase (AST): Often included to calculate the AST:ALT ratio, which can help identify specific liver conditions (ratio >2 strongly suggests alcoholic liver disease) 2

Synthetic Function Markers

• Albumin: Produced only by the liver; serves as a marker of synthetic function 1
• Prothrombin Time (PT)/International Normalized Ratio (INR): Assesses blood clotting function, which depends on liver-produced clotting factors 1, 2

Other Important Components

• Bilirubin (Total and Direct/Conjugated): Elevated in various liver and biliary conditions 1, 2
• Complete Blood Count (CBC): Particularly important for platelet count, as thrombocytopenia is the most common hematological abnormality in chronic liver disease 1

Clinical Utility and Interpretation

The Birmingham and Lambeth Liver Evaluation Testing Strategies (BALLETS) study found that ALT and ALP identified the vast majority of adults with liver disease 1. However, the addition of GGT increases sensitivity for detecting liver disease, particularly for alcohol-related liver disease (ARLD) and non-alcoholic fatty liver disease (NAFLD), which account for 90% of liver mortality 1.

Patterns of Abnormalities

• Hepatocellular pattern: Primarily elevated ALT and AST
• Cholestatic pattern: Primarily elevated ALP and GGT
• Mixed pattern: Elevations in both groups

Important Considerations

• The AST:ALT ratio >1 can indicate advanced fibrosis/cirrhosis 1
• Platelet count reduction is an indicator of advanced liver disease 1
• Albumin levels can be reduced in many clinical situations beyond liver disease (sepsis, inflammatory disorders, nephrotic syndrome) 1

Expanded Testing When Indicated

When abnormal liver function tests are detected, further testing may be warranted based on clinical suspicion:

Standard Liver Aetiology Panel

• Viral hepatitis: Hepatitis B surface antigen and hepatitis C antibody
• Iron overload: Ferritin and transferrin saturation
• Autoimmune liver disease: Anti-mitochondrial antibody, anti-smooth muscle antibody, antinuclear antibody, serum immunoglobulins 1

Extended Liver Aetiology Panel

• Metabolic liver disease: Alpha-1-antitrypsin level, thyroid function tests, caeruloplasmin
• Additional autoimmune markers: Anti-LKM antibody, coeliac antibodies 1

Clinical Pitfalls to Avoid

• Do not refer to these tests as "liver function tests" as most measure hepatocellular damage rather than function 3
• True liver function tests are those that measure protein synthesis (albumin, clotting factors) or the liver's capacity to metabolize drugs 3
• Avoid overinterpreting albumin as a marker of liver disease severity, as levels can be reduced in many non-hepatic conditions 1
• Remember that the magnitude of enzyme elevation may not correlate with the severity of liver injury 2

The optimal approach is to use a panel of tests rather than a single test due to superior sensitivity and specificity for liver disease 4. When investigating abnormal results, a restricted panel of ALT and ALP may be an efficient choice of analytes for excluding liver disease in primary care 5.