From the Guidelines
ALT is generally considered more reliable for detecting liver-specific damage, while elevated AST may indicate problems in other organs, as supported by the most recent study from 2023 1. When evaluating liver health, it's essential to consider the levels and ratio of AST and ALT.
- Normal ALT levels typically range from 7-56 U/L and AST from 10-40 U/L, though reference ranges vary by laboratory.
- The AST/ALT ratio can provide diagnostic clues - a ratio greater than 2:1 often suggests alcoholic liver disease, while ratios less than 1 typically occur in viral hepatitis and other liver conditions, as noted in a study from 2023 1.
- Both enzymes are released into the bloodstream when cells are damaged, with ALT remaining elevated longer than AST.
- These tests are commonly ordered together as part of liver function panels to diagnose conditions like hepatitis, fatty liver disease, medication-induced liver injury, and cirrhosis. The most recent and highest quality study from 2023 1 provides the most relevant information for making a definitive recommendation, prioritizing morbidity, mortality, and quality of life as the outcome.
- The study highlights the importance of considering the AST/ALT ratio in diagnosing liver diseases, such as alcoholic liver disease, which is supported by another study from 2016 1.
- The study also notes that ALT is more specific to liver injury, while AST is present in other organs, making ALT a more reliable indicator of liver-specific damage.
- The AST/ALT ratio can help differentiate between alcoholic liver disease and other liver conditions, such as viral hepatitis, as mentioned in a study from 2010 1.
From the Research
AST vs ALT
- AST (aspartate aminotransferase) and ALT (alanine aminotransferase) are two liver enzymes that are often measured together to assess liver health 2.
- Elevated levels of AST and ALT can indicate liver damage or disease, but the ratio of AST to ALT can help diagnose specific conditions 3.
- A study published in the Journal of Hepatology found that the evaluation of patients with elevated liver enzymes can be approached through either extensive testing or focused testing, depending on the patient's history and physical exam 4.
- In patients with severe alcoholic hepatitis, prednisolone treatment can increase susceptibility to infection and infection-related mortality, and is associated with high circulating levels of bacterial DNA 5.
- The diagnosis and treatment of alcohol-associated liver disease is a complex process, and liver transplantation may be necessary in severe cases 6.
- Elevated liver enzymes can be caused by a variety of factors, including viral hepatitis, genetic liver diseases, and drug-induced liver diseases 2.
- The interpretation of liver function tests (LFTs) requires an understanding of the biochemical basis of each test and an algorithmic approach to narrow the differential diagnosis 3.