From the Guidelines
Isolated AST elevation is most commonly caused by non-hepatic conditions such as muscle disorders, cardiac conditions, or hemolytic anemia, rather than liver disease, as suggested by the most recent study 1. When evaluating isolated AST elevation, it's essential to consider the following potential causes:
- Muscle disorders such as rhabdomyolysis, muscular dystrophy, or recent strenuous exercise, as AST is present in skeletal muscle while ALT is more liver-specific
- Cardiac conditions like myocardial infarction or heart failure can cause isolated AST elevation due to cardiac muscle damage
- Hemolytic anemia may elevate AST as it's present in red blood cells
- Certain medications like statins can cause muscle damage leading to isolated AST rise
- Less commonly, macro-AST (AST bound to immunoglobulins) can cause persistent elevation without underlying disease According to the study 1, the AST:ALT ratio can be helpful diagnostically - a ratio greater than 2:1 suggests muscle rather than liver pathology. It's also important to check creatine kinase (CK) levels to assess for muscle damage, review medication history, and consider cardiac testing if appropriate, as recommended in the study 2. Additionally, a thorough history of symptoms, co-existing medical conditions, concomitant medications, dietary and nutritional supplements, excessive exercise or muscle injury, alcohol consumption, and illicit substances should be taken, as outlined in the study 3. Treatment depends on addressing the underlying cause, such as modifying exercise habits, treating hemolysis, or adjusting medications that may be causing muscle damage.
From the Research
Causes of Isolated AST Rise
- Isolated elevation of aspartate aminotransferase (AST) can be caused by the presence of macro-aspartate aminotransferase (macro-AST), a rare and benign condition 4, 5
- Macro-AST is a high-molecular mass complex that can cause isolated AST elevation due to its difficulty in being cleared by the kidney 5
- The presence of macro-AST can be detected using laboratory methods such as precipitation with polyethylene glycol (PEG), ultracentrifugation, and gel filtration chromatography (GFC) 4
- Other causes of isolated AST rise may include autoimmune-associated chronic hepatitis C, which can be treated with ursodeoxycholic acid (UDCA) 6
- UDCA has been shown to improve liver function tests and reduce AST levels in patients with chronic hepatitis and autoimmune hepatitis 6, 7, 8
Detection and Diagnosis
- Early detection of macro-AST is important to avoid unnecessary investigations and treatments 4
- Laboratory tests such as PEG precipitation and alternative methods based on the low stability of macro-AST can be used to detect its presence 4
- Clinicians should be familiar with the rare condition of persistent isolated AST elevation due to macro-AST to provide appropriate diagnosis and treatment 5
Treatment and Management
- Treatment with UDCA has been shown to be effective in reducing AST levels and improving liver function in patients with autoimmune-associated chronic hepatitis C and autoimmune hepatitis 6, 7, 8
- The efficacy of UDCA in lowering serum AST and ALT levels is more pronounced in the presence of cirrhosis 7