From the Guidelines
When ALT is higher than AST, it typically suggests liver cell injury, most commonly due to conditions like viral hepatitis, medication-induced liver injury, or non-alcoholic fatty liver disease (NAFLD) 1. This pattern is significant because ALT is primarily found in liver cells, while AST is present in multiple tissues including heart, muscle, and liver. As a result, when liver cells are damaged, ALT leaks into the bloodstream in greater proportions than AST, creating this characteristic pattern that helps clinicians narrow down potential diagnoses.
Key Considerations
- The ALT>AST pattern is often seen in conditions such as viral hepatitis, medication-induced liver injury, or non-alcoholic fatty liver disease (NAFLD) 1.
- In contrast, alcoholic liver disease typically presents with an AST>ALT pattern 1.
- Initial management of elevated liver enzymes with ALT exceeding AST includes identifying and removing potential causes such as hepatotoxic medications, alcohol consumption, or high-fat diet 1.
- For NAFLD, lifestyle modifications including weight loss of 7-10% body weight, regular exercise (150 minutes weekly of moderate activity), and reducing carbohydrate and fat intake are recommended 1.
Clinical Implications
- The severity of abnormal aminotransferase can be classified as mild, moderate, or severe, with moderate and severe elevations indicating significant liver damage 1.
- Pathologically increased levels of ALP may occur in cholestatic liver disease, which can show elevated ALP with or without elevated bilirubin 1.
- It is essential to consult a healthcare provider for proper evaluation and management of elevated liver enzymes with ALT exceeding AST 1.
From the Research
Liver Enzyme Elevations
When Alanine Transaminase (ALT) is higher than Aspartate Transaminase (AST), it can indicate liver damage or disease. According to a study published in 2021 2, a higher ALT:AST ratio can be associated with immunotoxicity in patients treated with immune checkpoint inhibitors.
Causes of Elevated ALT
Elevated ALT can be caused by various factors, including:
- Hepatocellular damage 3
- Extrahepatic origin, such as muscle damage 3
- Immune checkpoint inhibitor immunotherapy 2
- Viral hepatitis 3
- Non-alcoholic steatosis 3
Comparison of ALT and AST
A study published in 2019 4 found that elevated AST was a better predictor of all-cause and liver-related mortality than elevated ALT. The study suggested that AST was associated with a higher risk of mortality and a greater loss of life expectancy than ALT.
Diagnostic Approach
When evaluating liver enzyme elevations, it is essential to consider the ratio of AST to ALT, as well as other liver function tests, such as alkaline phosphatase and gamma-glutamyl transferase 3. A hepatic enzyme pattern, characterized by predominant transaminase elevation, should be distinguished from a cholestatic pattern, characterized by predominant elevation of alkaline phosphatase and gamma-glutamyl transferase.
Limiting AST Testing
A study published in 2015 5 suggested that AST testing could be limited to cases where ALT exceeds a predetermined limit, reducing unnecessary testing and costs. However, this approach may not be applicable in all clinical situations, and the decision to test AST should be based on individual patient factors and clinical judgment.