Should I exercise caution with a mildly elevated Aspartate Aminotransferase (AST) level?

Evaluating Mildly Elevated AST of 37

A mildly elevated AST level of 37 generally does not require immediate medical intervention, but warrants appropriate monitoring and consideration of underlying causes, especially if persistent.

Understanding AST Elevation

AST (aspartate aminotransferase) is an enzyme found primarily in the liver, but also in heart, muscle, kidney, and brain tissue. When evaluating an AST of 37:

• This value is only slightly elevated above the normal range, which typically has an upper limit of normal (ULN) around 35 U/L in most laboratories 1
• Different populations may have different ULN values - a Korean study found AST ULN to be 32 U/L in men and 26 U/L in women 2
• Isolated mild AST elevations are common and often do not indicate significant liver disease

Clinical Approach to Mild AST Elevation

Step 1: Determine if this is an isolated finding

• Check other liver enzymes (ALT, alkaline phosphatase, GGT, bilirubin)
• Assess liver function (albumin, prothrombin time)
• An AST/ALT ratio >2 may suggest alcoholic liver disease 1

Step 2: Consider common causes of mild AST elevation

• Non-alcoholic fatty liver disease (NAFLD) - most common cause in developed countries
• Medication effects - many medications can cause mild transaminase elevations
• Alcohol consumption
• Muscle disorders or recent strenuous exercise (AST is also found in muscle tissue)
• Macro-AST (a benign condition where AST binds to immunoglobulins) 3

Step 3: Evaluate risk factors and symptoms

• Obesity, diabetes, hyperlipidemia (risk factors for NAFLD) 1
• Alcohol consumption history
• Current medications
• Presence of symptoms (fatigue, right upper quadrant pain, jaundice)

Recommendations for Follow-up

For an isolated AST of 37 with no symptoms:

1. Repeat testing in 2-3 months to determine if elevation is persistent
2. If persistent elevation:
   • Conduct serologic testing for common liver diseases (hepatitis B, hepatitis C)
   • Consider ultrasound of the liver if risk factors for NAFLD are present
   • Evaluate alcohol consumption and medication use

Special Considerations

• If taking medications known to affect liver enzymes, discuss with your prescribing physician
• If you have risk factors for NAFLD (obesity, diabetes, metabolic syndrome), lifestyle modifications may be beneficial
• Avoid alcohol if there's concern for alcoholic liver disease

When to Be More Concerned

More urgent evaluation is needed if:

• AST rises to >3x ULN (>105 U/L) 1
• Other liver enzymes are significantly elevated
• Symptoms of liver disease develop (jaundice, abdominal pain, etc.)
• You have known chronic liver disease

Remember that extreme AST elevations (>3000 U/L) are typically associated with severe conditions like ischemic/hypoxic hepatitis and carry high mortality 4, but this is not relevant to your mild elevation of 37.