What SGOT and SGPT Tell You
SGOT (AST) and SGPT (ALT) are enzymes that indicate hepatocellular injury when elevated, with ALT being highly specific for liver damage while AST can be elevated from cardiac, skeletal muscle, kidney, and red blood cell disorders. 1
Primary Clinical Significance
ALT (SGPT) - The Liver-Specific Marker
- ALT is the most specific marker for liver injury because it is concentrated primarily in the liver with minimal presence in skeletal muscle and kidney 1, 2
- Normal ALT levels are 29-33 IU/L in men and 19-25 IU/L in women 1, 2
- ALT elevations directly indicate hepatocyte injury and necrosis, making it the preferred marker for diagnosing and monitoring liver disease 1
AST (SGOT) - Less Specific but Still Important
- AST is less specific for liver injury because it is also present in cardiac muscle, skeletal muscle, kidneys, brain, and red blood cells 1
- AST elevations could indicate disorders involving the heart, skeletal muscle, kidneys, or hemolysis in addition to liver disease 1
- When AST is elevated in isolation or disproportionately to ALT, consider non-hepatic sources such as muscle injury or cardiac disease 3
Interpreting the AST/ALT Ratio
Hepatocellular Pattern (AST/ALT <1)
- An AST/ALT ratio less than 1 is characteristic of nonalcoholic fatty liver disease (NAFLD), viral hepatitis, or medication-induced liver injury 2
- This pattern indicates typical hepatocellular injury where ALT rises more than AST 2
Alcoholic Liver Disease Pattern (AST/ALT >2)
- In approximately 70% of patients with alcoholic liver disease, the AST/ALT ratio is higher than 2 1
- Ratios greater than 3 are highly suggestive of alcoholic liver disease 1
- This occurs because alcohol depletes pyridoxine (vitamin B6), which is required for ALT synthesis, and because AST is released from mitochondria in alcoholic hepatitis 1
Severity Classification
Mild Elevation
- Less than 5 times the upper reference limit 1
- Common causes include fatty liver disease, chronic viral hepatitis, and medication effects 1
Moderate Elevation
- 5 to 10 times the upper reference limit 1
- Suggests more significant hepatocellular injury requiring further investigation 1
Severe Elevation
- Greater than 10 times the upper reference limit 1
- AST levels more than 500 IU/L or ALT more than 200 IU/L are uncommon in alcoholic hepatitis alone and should prompt evaluation for other causes such as acute viral hepatitis, ischemic hepatitis, or acetaminophen toxicity 1
Common Causes of Elevation
Hepatocellular Injury (Both Elevated)
- Fatty liver disease (NAFLD/NASH) - most common cause in patients with metabolic risk factors 2
- Acute or chronic viral hepatitis (hepatitis B, C, E) 1, 2
- Medication-induced liver injury from prescription drugs, over-the-counter medications, or herbal supplements 2
- Autoimmune hepatitis 1
- Ischemic hepatitis (shock liver) 1
- Hemochromatosis, Wilson disease, alpha-1 antitrypsin deficiency 1
Isolated AST Elevation
- Cardiac disease (myocardial infarction) 3
- Skeletal muscle injury or myopathy 1, 4
- Hemolysis 1
- Macro-AST (benign condition where AST binds to immunoglobulins) 5
Important Clinical Pitfalls
Don't Assume All Transaminase Elevations Are Liver Disease
- Always check creatine kinase (CK) when AST is disproportionately elevated to rule out muscle disorders 2
- Consider cardiac causes in patients with chest pain or cardiovascular risk factors 3
- In patients with inflammatory myopathies, both AST and ALT can be elevated due to muscle injury, not liver disease 4
Normal Transaminases Don't Exclude Liver Disease
- Albumin and prothrombin time are actual markers of hepatocellular synthetic function, not AST/ALT 1
- Patients with cirrhosis may have normal or only mildly elevated transaminases despite advanced disease 1
Context Matters for Interpretation
- In blunt abdominal trauma, SGOT above 110.5 U/L and SGPT above 63.5 U/L indicate intra-abdominal injury, with levels above 500 U/L (SGOT) and 300 U/L (SGPT) suggesting severe hepatic injury 6
- In alcoholic liver disease, GGT is commonly elevated alongside transaminases and may be more sensitive for detecting chronic alcohol consumption 1
Recommended Diagnostic Approach
Initial Evaluation
- Obtain complete liver panel including AST, ALT, alkaline phosphatase, total and direct bilirubin, albumin, and prothrombin time 2
- Assess for metabolic syndrome components (obesity, diabetes, hypertension) as risk factors for NAFLD 2
- Take detailed alcohol consumption history and complete medication review including over-the-counter drugs and supplements 2
- Perform viral hepatitis serologies (HBsAg, HBcIgM, HCV antibody) 2
When to Image
- Abdominal ultrasound is the first-line imaging test for evaluating transaminase elevations, with 84.8% sensitivity and 93.6% specificity for detecting moderate to severe hepatic steatosis 2
- Ultrasound can identify structural causes including biliary obstruction, focal lesions, and fatty infiltration 2
When to Refer
- Consider hepatology referral if transaminases remain elevated for ≥6 months without identified cause 2
- Refer if there is evidence of synthetic dysfunction (low albumin, prolonged PT/INR) 2
- Urgent referral needed if ALT increases to >5× upper limit of normal or if accompanied by bilirubin >2× upper limit of normal 2