Is Aspartate Aminotransferase (AST) or Alanine Aminotransferase (ALT) higher in alcoholic hepatitis?

AST is Higher than ALT in Alcoholic Hepatitis

In alcoholic hepatitis, AST (aspartate aminotransferase) is typically higher than ALT (alanine aminotransferase), with an AST/ALT ratio greater than 2 being highly suggestive of alcoholic liver disease.

Laboratory Pattern in Alcoholic Hepatitis

AST/ALT Ratio

• AST elevation is more prominent than ALT in alcoholic hepatitis 1
• An AST/ALT ratio exceeding 2 strongly suggests alcoholic hepatitis 1
• When the ratio exceeds 3, it is considered highly specific for alcoholic liver disease 1
• According to a large series review, AST/ALT ratios <1.5 are seen in <2% of patients with histologically proven alcoholic hepatitis 1

Typical Enzyme Patterns

• AST is typically elevated 2-6 times the upper limits of normal 1, 2
• ALT is usually lower than AST in alcoholic liver disease 1, 2
• Both AST and ALT levels usually do not exceed 300-400 IU/L in alcoholic hepatitis 1
• Values above these thresholds should prompt consideration of other diagnoses such as drug-induced liver injury or ischemic hepatitis 1

Mechanisms and Clinical Significance

Why AST is Higher than ALT

• The higher AST/ALT ratio in alcoholic hepatitis reflects the pattern and severity of liver damage caused by alcohol
• AST has a shorter half-life (18 hours) compared to ALT (36 hours), but is released in greater quantities in alcohol-induced hepatocellular injury 3
• The ratio increases with disease progression, particularly when cirrhosis develops 4

Diagnostic Value

• The AST/ALT ratio helps differentiate alcoholic liver disease from other liver conditions:
  • Non-alcoholic steatohepatitis (NASH) typically has a ratio <1 5
  • Viral hepatitis usually has ALT higher than AST (ratio <1)
  • An AST/ALT ratio ≥2 is strongly suggestive of alcoholic liver disease 5

Clinical Application

Interpreting the Ratio in Context

• The AST/ALT ratio should be interpreted alongside:
  • History of alcohol consumption
  • Other laboratory markers (GGT, MCV, bilirubin)
  • Clinical presentation (jaundice, tender hepatomegaly)
  • Exclusion of other causes of liver disease

Limitations and Pitfalls

• The ratio may be affected by:
  • Time elapsed since alcohol exposure 3
  • Presence of cirrhosis (which can elevate the ratio regardless of etiology) 4
  • Vitamin B6 (pyridoxal phosphate) deficiency, which is common in alcoholics and affects transaminase activity 3
  • Multiple concurrent liver pathologies

Monitoring and Prognosis

• The AST/ALT ratio may increase with progression of fibrosis
• In patients with alcoholic hepatitis and cirrhosis, the ratio tends to be higher (mean 2.68) compared to those without cirrhosis (mean 1.47) 4
• Regular monitoring of this ratio can help assess response to alcohol abstinence

In summary, while no single laboratory test definitively establishes alcohol as the etiology of liver disease, the characteristic pattern of AST being higher than ALT with an AST/ALT ratio >2 is a valuable diagnostic clue for alcoholic hepatitis.