What is the significance of the aspartate aminotransferase (AST)/alanine aminotransferase (ALT) ratio in evaluating liver injury?

From the Guidelines

The AST/ALT ratio is a crucial diagnostic tool in evaluating liver injury, with a ratio greater than 2 strongly indicating alcoholic liver disease, as supported by the most recent study 1.

Significance of AST/ALT Ratio

The AST/ALT ratio is significant in differentiating types of liver injury and disease severity.

• A ratio less than 1 typically suggests acute viral hepatitis, drug-induced liver injury, or non-alcoholic fatty liver disease.
• A ratio greater than 2 strongly indicates alcoholic liver disease, as seen in the study 1, where ratios greater than 3 are highly suggestive of ALD.
• In cirrhosis, the ratio often exceeds 1 regardless of etiology.

Mechanism and Interpretation

The De Ritis ratio (AST/ALT) works because AST is present in multiple tissues (liver, heart, muscle, kidney) while ALT is more liver-specific.

• In alcoholic liver disease, mitochondrial AST is released due to alcohol's toxic effects, elevating the ratio.
• ALT levels may be lower in chronic liver disease due to vitamin B6 deficiency, which affects ALT synthesis.
• The ratio should be interpreted alongside clinical context, other liver function tests, and imaging studies, as various factors like medication use, muscle injury, or hemolysis can affect transaminase levels independently of liver pathology.

Clinical Application

Serial measurements of the AST/ALT ratio often provide more valuable information than a single reading, as seen in the study 1, where the diagnosis of ALD is frequently suspected upon documentation of excess alcohol consumption and the presence of clinical and/or biological abnormalities suggestive of liver injury.

• The AST/ALT ratio is not the only diagnostic tool, and other laboratory markers such as carbohydrate deficient transferrin (CDT) and GGT can also be used to detect previous alcohol consumption 1.
• However, the AST/ALT ratio remains a valuable tool in the diagnosis and management of liver disease, particularly in differentiating between alcoholic and non-alcoholic liver disease.

From the Research

Significance of AST/ALT Ratio

The AST/ALT ratio is a significant indicator in evaluating liver injury, particularly in distinguishing between alcoholic liver disease (ALD) and non-alcoholic liver disease.

• The ratio is usually greater than 2.0 in ALD and less than 1.0 in patients with chronic hepatitis and chronic cholestatic syndromes 2.
• An AST/ALT ratio greater than 1.0 in a patient with non-alcoholic liver disease may suggest the presence of cirrhosis 2.
• However, the AST/ALT ratio may not be helpful in distinguishing between ALD and non-alcoholic liver disease in the presence of cirrhosis 2.

AST/ALT Ratio in Alcoholic Liver Disease

• The AST/ALT ratio is often elevated in patients with alcoholic liver disease, with a ratio greater than 2 being highly suggestive of alcoholic hepatitis and cirrhosis 3.
• The ratio is significantly elevated in patients with alcoholic hepatitis and cirrhosis compared to patients with postnecrotic cirrhosis, chronic hepatitis, obstructive jaundice, and viral hepatitis 3.
• The GOT/GPT ratio in liver tissue is increased in patients with alcoholic liver cirrhosis and alcoholic liver disease 4.

Limitations of AST/ALT Ratio

• The AST/ALT ratio may not be reliable in distinguishing between ALD and autoimmune hepatitis (AIH) in patients with increased alcohol consumption 5.
• The ratio may not be helpful in discriminating between AIH and ALD in patients with both conditions 5.
• Reliable autoantibody testing and cautious interpretation of liver histology are necessary for AIH diagnosis in patients with increased alcohol consumption 5.