AST is Typically Elevated More Than ALT in Cirrhosis
In cirrhosis, aspartate transaminase (AST) is characteristically elevated to a greater degree than alanine transaminase (ALT), resulting in an AST/ALT ratio typically greater than 1.0. This reversal of the normal ratio represents a key biochemical marker of advanced liver disease and cirrhotic transformation.
The AST/ALT Ratio in Cirrhosis
The AST/ALT ratio rises to greater than 1.0 when cirrhosis first becomes manifest in patients with chronic liver disease 1
In chronic hepatitis B patients without cirrhosis, the mean AST/ALT ratio is 0.59, but this increases to 1.02 in those with established cirrhosis 1
An AST/ALT ratio ≥1.0 in patients with nonalcoholic liver disease is highly suggestive of underlying cirrhosis 1, 2
The ratio increases progressively with histological advancement of liver fibrosis, making it a useful marker for disease progression 2, 3
Why AST Predominates in Cirrhosis
The elevated AST/ALT ratio in cirrhosis reflects both the time course and aggressiveness of chronic liver injury 3
AST has a shorter half-life (18 hours) compared to ALT (36 hours), and in advanced disease with ongoing hepatocellular damage, AST release predominates 3
In cirrhotic patients with acute exacerbation, an AST/ALT ratio >1.38 is independently associated with increased risk of 90-day adverse outcomes including death or liver transplantation 4
Clinical Context and Interpretation
While ALT is more liver-specific than AST under normal circumstances, the AST/ALT ratio becomes a more important diagnostic and prognostic marker in advanced liver disease 5, 1
AST is present not only in liver tissue but also in cardiac muscle, skeletal muscle, and erythrocytes, making it less specific for liver injury in isolation 6
However, when both enzymes are elevated with AST predominating (ratio >1), this pattern strongly suggests cirrhotic transformation regardless of the underlying etiology 1, 2
Important Caveats
The AST/ALT ratio must be interpreted in clinical context—alcoholic liver disease typically shows ratios >2.0, while the ratio in cirrhosis from other causes is usually between 1.0-2.0 7, 8
In advanced alcoholic liver disease specifically, the AST/ALT ratio is characteristically greater than 2, with ratios >3 being highly specific for alcoholic etiology 7, 8
The use of AST/ALT ratio to distinguish alcoholic from nonalcoholic liver disease becomes less reliable in the presence of cirrhosis, as both conditions may show elevated ratios 1
AST levels rarely exceed 300 IU/mL in cirrhosis, and levels >500 IU/mL should prompt consideration of alternative or additional diagnoses 7
Additional Markers of Advanced Disease
When cirrhosis develops, additional biochemical changes occur including progressive decline in serum albumin, prolongation of prothrombin time, and thrombocytopenia 7
These synthetic function markers, combined with the reversed AST/ALT ratio, provide comprehensive assessment of cirrhotic liver disease 7