From the Guidelines
Elevated AST levels with normal ALT levels can indicate muscle damage, heart injury, hemolysis, or certain medications, rather than liver disease, and require further evaluation with tests such as creatine kinase, cardiac troponin, or complete blood count to determine the underlying cause. When interpreting abnormal liver chemistry tests, it is essential to consider the clinical context of the patient, including their medical history, medications, and physical examination findings, as stated in the american gastroenterological association medical position statement 1. The evaluation of patients with AST elevations should be directed toward establishing a diagnosis based on the specific clinical scenario, rather than following an algorithm. Some possible causes of elevated AST with normal ALT include:
- Muscle damage or disorders, such as muscular dystrophy
- Heart injury, such as a heart attack
- Hemolysis, or red blood cell destruction
- Certain medications or alcohol use The ratio of AST to ALT, known as the De Ritis ratio, can provide diagnostic clues, with a ratio greater than 2 often suggesting alcohol-related liver disease or muscle injury rather than viral hepatitis or other liver conditions. It is crucial to discuss these findings with a healthcare provider to determine the underlying cause and appropriate management, as the interpretation of abnormal liver chemistries must be taken in the clinical context of a given patient 1.
From the Research
Elevated AST with Normal ALT
- An elevated Aspartate Aminotransferase (AST) level with a normal Alanine Aminotransferase (ALT) level can indicate non-hepatic causes of AST elevation, as AST is also present in cardiac and skeletal muscle and in erythrocytes 2.
- This pattern of liver enzyme elevation can be seen in patients with acute ST-elevation myocardial infarction (STEMI), where AST is elevated above the upper limit of normal in 85.6% of patients, while ALT is elevated in 48.2% of patients at baseline or day 1 3.
- In patients treated with checkpoint inhibitor immunotherapy, liver enzyme elevation is common, but often has a cause other than immunotoxicity, and a biochemical signature with higher ALT and ALT/AST ratio may help to identify patients at a higher likelihood of immunotoxicity 4.
- Non-hepatic causes of raised AST include acute myocardial infarction, polymyositis, and acute muscle injury, and the primary care doctor should obtain a complete history regarding the risk factors for these conditions and request investigations accordingly 5.
- In some cases, an elevated AST level with a normal ALT level may not have a clear cause, and further evaluation and monitoring may be necessary to determine the underlying cause of the elevation 6.