From the Guidelines
Elevated AST with normal ALT suggests a need for further evaluation to determine the underlying cause, as AST elevations can be due to various conditions, including liver damage, heart, skeletal muscle, kidneys, brain, and red blood cells disorders, and the severity of abnormal aminotransferase levels should be classified to guide management. The severity of abnormal aminotransferase can be classified as mild, moderate, or severe, with moderate and severe categories having significant clinical overlap 1.
Key Considerations
- AST elevations are not specific to liver injury and can be caused by various conditions, including heart, skeletal muscle, kidneys, brain, and red blood cells disorders 1
- The severity of abnormal aminotransferase levels should be classified to guide management, with levels <5 times the upper reference limit considered mild, 5 to 10 times considered moderate, and >10 times considered severe 1
- Medical evaluation is necessary to determine the specific cause of elevated AST, which may include blood tests, imaging studies, and other diagnostic tests
Management
- Lifestyle modifications, such as weight loss if overweight, limiting alcohol consumption, regular exercise, and a balanced diet, may be recommended to address underlying conditions that may be contributing to elevated AST 1
- Treatment depends on the underlying cause, ranging from lifestyle changes to medical interventions, such as discontinuation of hepatotoxic medications or antiviral medications for viral hepatitis
- Regular monitoring of liver enzymes is important to track progress and response to interventions 1
Diagnostic Clues
- The ALT/AST ratio can provide diagnostic clues, although in this case, ALT is normal, which may limit the usefulness of this ratio
- Other laboratory tests, such as alkaline phosphatase (ALP) and bilirubin, may be helpful in determining the underlying cause of elevated AST 1
From the Research
Elevated ALT and AST Levels
Elevated alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels are commonly used biomarkers for liver damage 2. The following are some key points to consider:
- ALT is the most specific marker for liver damage, while AST is also present in cardiac and skeletal muscle and in erythrocytes 2.
- Elevated ALT and AST levels can be caused by various factors, including non-alcoholic fatty liver disease (NAFLD) 3, 4, 5.
- NAFLD is one of the most common causes of chronic liver disease, characterized by a variety of pathologies, ranging from benign fatty liver to extensive fibrosis and even hepatocellular cancer 5.
Treatment Options
Some treatment options for elevated ALT and AST levels include:
- Metformin, which has been shown to decrease the sonography grade of NAFLD and reduce the levels of ALT and AST 3, 4.
- Pioglitazone, which has been shown to improve biochemical indices in patients with NAFLD, although its effect on liver enzymes is less significant compared to metformin 3, 4.
- Vitamin E, which has been shown to improve biochemical and histological abnormalities in NAFLD, although its effect on liver fibrosis is limited 5.
- Silymarin, which has been shown to reduce the levels of AST and ALT in patients with NAFLD 4.
Evaluation and Diagnosis
The evaluation of abnormal liver chemistries, including ALT and AST levels, should involve the following steps:
- Assessment of hepatocellular injury, including testing for viral hepatitis, non-alcoholic fatty liver disease, and alcoholic liver disease 6.
- Screening for hereditary hemochromatosis, autoimmune hepatitis, Wilson's disease, and alpha-1 antitrypsin deficiency 6.
- Evaluation of alkaline phosphatase elevation, including testing for primary biliary cholangitis and primary sclerosing cholangitis 6.
- Fractionation of total bilirubin elevation to direct and indirect bilirubin fractions, and consideration of liver biopsy when serologic testing and imaging fails to elucidate a diagnosis 6.