What are the results of the Aspartate Aminotransferase (AST or SGOT) and Alanine Aminotransferase (ALT or SGPT) exams?

From the Guidelines

Elevated levels of Aspartate Aminotransferase (AST) and Alanine Aminotransferase (ALT) indicate liver damage, which can be caused by various conditions such as hepatitis, fatty liver disease, alcohol abuse, or medication toxicity, as reported in the most recent study 1. The normal range for AST is typically 5-40 units per liter and for ALT is 7-56 units per liter, though reference ranges may vary slightly between laboratories. To prepare for these tests, patients should fast for 8-12 hours beforehand and inform their doctor about any medications they're taking, as some can affect results. The test involves a simple blood draw from a vein, usually in the arm, and results are generally available within 24 hours. Some key points to consider when interpreting AST and ALT results include:

• Elevated levels of AST and ALT can indicate liver damage, but the severity of the damage can vary, with mild increases being more common in nonalcoholic fatty liver disease (NAFLD) and alcohol-induced liver disease, as noted in 1.
• The AST:ALT ratio can help differentiate between alcohol-induced fatty liver disease (ratio >2) and metabolic disease-related fatty liver (ratio <1), as discussed in 1.
• ALT elevations are more specific for liver injury, whereas AST elevations can also be caused by non-hepatic conditions such as heart or muscle damage, as mentioned in 1.
• The severity of abnormal aminotransferase levels can be classified as mild, moderate, or severe, with moderate and severe elevations indicating more significant liver damage, as described in 1. It is essential to interpret AST and ALT results in the clinical context of the patient, considering their medical history, medications, and physical examination, as emphasized in 1. If AST and ALT levels are abnormal, the doctor will likely recommend additional tests to determine the underlying cause of the liver damage. These enzymes are released into the bloodstream when liver cells are damaged, making them valuable markers for liver health assessment, as reported in 1 and 1.

From the Research

Results of AST and ALT Exams

The results of the Aspartate Aminotransferase (AST or SGOT) and Alanine Aminotransferase (ALT or SGPT) exams can indicate liver injury or disease.

• Elevated AST and ALT levels can be associated with liver damage, as seen in patients with blunt abdominal trauma 2.
• In patients with elevated ALT levels, even small amounts of alcohol intake may be harmful, and are associated with increased liver-related and all-cause mortality 3.
• The interpretation of ALT and AST plasma levels can be complicated, and both have poor prognostic utility in acute liver injury and liver failure 4.
• Low-cost point-of-care monitoring of ALT and AST is promising for faster decision making and diagnosis of acute liver injury 5.

Liver Function Values

Liver function values, including AST and ALT, can be affected by various factors, such as:

• Total parenteral nutrition (TPN), which can cause a "meaningful" increase in SGOT levels in 68% of patients 6.
• Blunt abdominal trauma, where abnormal hepatic transaminase levels are associated with liver injuries 2.
• Alcohol intake, which can be harmful in subjects with elevated ALT levels 3.

Diagnostic Utility

The diagnostic utility of AST and ALT exams can be improved by:

• Using low-cost biosensing methods, such as paper-based assays, for the analysis of ALT and AST levels in biological fluids 5.
• Combining AST and ALT exams with other laboratory tests, such as lactate dehydrogenase (LDH) and γ-glutamyl transpeptidase (GGT), to predict the presence of liver injury 2.