What does it mean when Alanine Transaminase (ALT) is greater than Aspartate Transaminase (AST)?

From the Guidelines

When ALT is greater than AST, it typically suggests liver disease, particularly conditions affecting the hepatocytes, such as viral hepatitis, drug-induced liver injury, and non-alcoholic fatty liver disease (NAFLD) 1. This pattern is commonly seen in conditions where hepatocyte injury is the primary cause of liver damage. The reason ALT tends to be higher than AST in these conditions is because ALT is primarily found in the liver, while AST is present in multiple tissues including the liver, heart, muscles, kidneys, and brain 1.

Key Points to Consider

• The AST:ALT ratio is generally >2 in alcohol-induced fatty liver disease and <1 in metabolic disease-related fatty liver 1.
• ALT elevations are specific for liver injury owing to low concentrations in skeletal muscle and kidney 1.
• The severity of abnormal aminotransferase can be classified as mild, moderate, or severe, with mild being <5 times the upper reference limit, moderate being 5 to 10 times the upper reference limit, and severe being >10 times the upper reference limit 1.
• Further evaluation is recommended, including a complete liver panel, viral hepatitis screening, and possibly imaging studies like ultrasound, to determine the underlying cause of the ALT>AST pattern.
• Lifestyle modifications such as avoiding alcohol, maintaining a healthy weight, and discontinuing potentially hepatotoxic medications may be advised depending on the underlying cause 1.

Important Considerations for Patient Care

• The degree of elevation is also important, with mild elevations often indicating chronic conditions and marked elevations suggesting acute hepatocellular injury 1.
• It is essential to consider the patient's medical history, physical examination, and other laboratory results to determine the underlying cause of the ALT>AST pattern and provide appropriate management and treatment.

From the Research

Alanine Transaminase (ALT) and Aspartate Transaminase (AST) Ratio

• The ratio of AST to ALT is often used as a clue to the etiology of the underlying liver disease 2.
• A ratio of less than 1.0 is typically seen in patients with chronic hepatitis and chronic cholestatic syndromes, while a ratio greater than 2.0 is often associated with alcoholic liver disease 2.
• When ALT is greater than AST, the AST/ALT ratio is less than 1.0, which is commonly observed in non-alcoholic liver disease, such as chronic viral hepatitis 2, 3.

Clinical Implications

• An AST/ALT ratio of greater than 1.0 in a patient with non-alcoholic liver disease may suggest the presence of cirrhosis 2, 3.
• Both ALT and AST are useful markers for chronic hepatitis C, and the AST/ALT ratio increases with liver histological progression 3.
• Measuring AST may be useful when the ALT is consistently normal, as AST may elevate alone in some cases 3.

Liver Disease Etiology

• The differential diagnosis of an increase in ALT and/or AST level often includes ischemic hepatitis, acute viral hepatitis, and drug-induced liver injury 4.
• The most common causes of acute liver injury and their relative frequencies may vary depending on the hospital type and patient population 4.