From the Guidelines
AST and ALT values are considered significant when they exceed 5 times the upper reference limit, indicating moderate to severe liver injury, as stated in the most recent study 1. The severity of abnormal aminotransferase can be classified as mild, moderate, or severe, with moderate and severe being considered significant due to clinical overlap between these categories.
- Mild elevations are typically less than 5 times the upper reference limit,
- Moderate elevations range from 5 to 10 times the upper reference limit,
- Severe elevations are greater than 10 times the upper reference limit. It's essential to consider the pattern of elevation, with ALT being more specific to liver damage, while AST can be elevated in muscle or cardiac injury as well. The AST/ALT ratio can provide diagnostic clues, with a ratio greater than 2 often suggesting alcoholic liver disease, while a ratio less than 1 is more typical of viral hepatitis or fatty liver disease, as supported by previous studies 1. When evaluating these enzymes, it's crucial to consider the patient's symptoms, medical history, medication use, and other laboratory values like bilirubin, alkaline phosphatase, and albumin to determine the clinical significance and appropriate management. According to the most recent guidelines 1, normal ALT levels are 29 to 33 IU/L in men and 19 to 25 IU/L in women, and these values should be used as a reference when assessing the significance of AST and ALT elevations.
From the Research
AST and ALT Significance
- Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) values are considered significant when they exceed certain thresholds, indicating potential liver damage or disease 2, 3, 4, 5, 6.
Thresholds for Significance
- Clinically significant drug-induced liver injury (DILI) is defined by elevations of ALT ≥5 times the upper limit of normal (ULN), alkaline phosphatase (ALP) ≥2 × ULN, or ALT ≥3 × ULN and total bilirubin TBIL >2 × ULN 2.
- Elevation of serum levels of AST and ALT to more than 130 IU/L is a marker for intra-abdominal injury, with higher enzyme levels more frequently associated with liver injury 3.
- ALT levels > 3 × UNL are not recommended for prescription of statins, but studies have shown that statins can be prescribed without deleterious effects in patients with ALT > 3 times the UNL 4.
- Marked elevation of serum transaminase in patients with acute gallstone disease might be due to an acute inflammatory liver cell injury caused by impacted bile duct stones or migrating stones, which would be transient and reversible after early resolution of the bile duct obstruction 5.
Clinical Implications
- The determination of serum transaminase activity could offer a routine and rapid laboratory test for establishing the presence of hepatic cellular damage following intrauterine or perinatal asphyxia, with a correlation between hypoxia and the increase in serum activity of transaminases in full-term and premature asphyxiated newborns 6.