What are the levels of Aspartate Aminotransferase (AST) and Alanine Aminotransferase (ALT) in alcoholic liver disease?

Transaminase Pattern in Alcoholic Liver Disease

In alcoholic liver disease, the AST/ALT ratio is typically greater than 2, with AST levels rarely exceeding 300 IU/ml and ALT levels commonly lower than AST. 1, 2

Characteristic Transaminase Pattern

Alcoholic liver disease presents with a distinctive pattern of liver enzymes:

• AST (Aspartate Aminotransferase):

  • Moderately elevated (average ~59 ± 34 U/L) 3
  • Rarely exceeds 300 IU/ml 1
  • Has a sensitivity of 50% and specificity of around 80% for ALD 1

• ALT (Alanine Aminotransferase):

  • Usually lower than AST (average ~27 ± 13 U/L) 3
  • Often within normal range even in advanced disease 3

• AST/ALT Ratio:

  • Typically greater than 2 in alcoholic liver disease 1, 2
  • Ratio greater than 3 is even more specific for alcoholic etiology 2
  • Increases with disease severity - mean ratio of 1.68 in Child A, 2.28 in Child B, and 3.03 in Child C patients 4

Mechanism Behind the Elevated AST/ALT Ratio

The characteristic AST/ALT ratio >2 in alcoholic liver disease occurs due to:

• Alcohol-induced pyridoxine (vitamin B6) deficiency, which reduces ALT activity more than AST activity
• Increased mitochondrial AST release from damaged hepatocytes
• Alcohol's direct hepatotoxic effect causing mitochondrial injury

Clinical Significance

This transaminase pattern is clinically significant for several reasons:

• Diagnostic Value: The AST/ALT ratio >2 helps differentiate alcoholic liver disease from other liver conditions 1, 5

  • In non-alcoholic steatohepatitis (NASH), the ratio is typically <1 5
  • In viral hepatitis, the ratio is usually <1 unless cirrhosis develops 6

• Disease Severity Indicator: The AST/ALT ratio increases with worsening liver disease, correlating with Child-Pugh classification 4

• Caution in Interpretation:

  • Aminotransferase levels may be normal or near normal in patients with alcoholic cirrhosis 3
  • The AST/ALT ratio may be >1 in non-alcoholic liver disease when cirrhosis develops 6

Other Laboratory Findings in Alcoholic Liver Disease

Beyond transaminases, other laboratory findings include:

• Elevated GGT (sensitivity 73% for detecting alcohol consumption >50g/day) 1
• Elevated MCV (sensitivity 52%) 1
• Decreased albumin in advanced disease 1
• Prolonged prothrombin time in advanced disease 1
• Elevated bilirubin in advanced disease 1

Clinical Pitfalls

• Normal enzymes don't rule out disease: Aminotransferase levels can be unremarkable even in advanced alcoholic cirrhosis and bear no relationship to clinical outcomes 3
• AST elevation sources: AST is not liver-specific and can be elevated due to muscle injury, hemolysis, or other conditions 7
• Ratio changes with progression: The AST/ALT ratio may increase above 1.0 when cirrhosis develops, even in non-alcoholic liver disease 6
• Comorbidities impact: Obesity, diabetes, and other conditions can alter the typical pattern 2

The transaminase pattern, particularly the AST/ALT ratio, remains a valuable diagnostic tool for alcoholic liver disease but must be interpreted in the context of the patient's complete clinical picture.