In a patient with asthma who has mildly elevated alanine aminotransferase (ALT) levels of 46 and 61 U/L, what management steps should be taken?

Investigate the cause of the mildly elevated ALT rather than simply repeating the test, while continuing asthma management as indicated by disease control

In an asthma patient with ALT levels of 46 and 61 U/L (mildly elevated), you should obtain a thorough clinical history and perform a core liver aetiology screen to identify the underlying cause, rather than just monitoring the values. 1

Why Investigation is Necessary

The 2018 Gut guidelines on abnormal liver blood tests are clear: when liver enzymes are elevated, 84% remain abnormal at 1 month and 75% at 2 years 1. Simply repeating the same tests is not recommended unless there's high clinical suspicion of a transient finding. Your patient has two elevated values (46 and 61 U/L), suggesting this is not a transient elevation.

Specific History to Obtain

Focus your history on these key elements 1:

• Medications: All asthma medications (particularly leukotriene inhibitors like zileuton which require liver monitoring per asthma guidelines 2), over-the-counter drugs, herbals, and supplements
• Metabolic risk factors: Central obesity, hypertension, diabetes, dyslipidemia (NAFLD is common)
• Alcohol intake: Quantify in units per week using AUDIT-C
• Viral hepatitis risk: Ethnicity, country of birth, travel history, injection drug use
• Other causes: Recent muscle injury, tick bites, occupational exposures
• Symptoms: Jaundice, abdominal pain, weight loss, pruritus

Physical Examination Priorities

• BMI calculation
• Abdominal exam: Hepatosplenomegaly, ascites, signs of chronic liver disease

Core Laboratory Panel

Order a standard liver aetiology screen 1:

• Hepatitis B surface antigen (HBsAg)
• Hepatitis C antibody
• Autoimmune markers (ANA, anti-smooth muscle antibody, immunoglobulins)
• Ferritin and transferrin saturation
• Fasting glucose and lipid panel
• Repeat liver function tests including ALT, AST, alkaline phosphatase, bilirubin, albumin

Context: ALT Levels and Significance

Your patient's ALT of 46-61 U/L represents mild elevation (not the >1000 U/L that triggers acute viral hepatitis workup) 1. Note that updated definitions suggest normal ALT upper limits should be 30 U/L for men and 19 U/L for women 3, making your patient's values more clinically significant than older reference ranges suggest.

Asthma-Specific Considerations

If your patient is on zileuton (a leukotriene inhibitor), this is particularly relevant as the EPR-3 asthma guidelines specifically note it's a "less desirable alternative because of limited studies as adjunctive therapy and the need to monitor liver function" 2. Consider switching to a preferred therapy if zileuton is the cause.

Research shows that asthma patients can have considerable variability in liver chemistries even without common drug therapy 4, but this doesn't negate the need for investigation. Additionally, elevated AST/ALT ratios in asthma patients are associated with increased all-cause mortality, particularly in those over 40 years 5.

Continue Asthma Management

While investigating the ALT elevation, continue managing asthma according to the stepwise approach based on current control level 2:

• Assess control using impairment (symptoms, rescue inhaler use >2 days/week, nighttime awakenings) and risk domains (exacerbations)
• Adjust therapy step up or down every 2-6 weeks based on control
• Avoid or discontinue zileuton if being used

When to Refer

Refer to hepatology/gastroenterology if 1:

• Positive viral hepatitis markers (HBsAg, HCV antibody with positive PCR)
• Evidence of autoimmune hepatitis
• Ferritin elevated with transferrin saturation >45% (hemochromatosis)
• Unexplained jaundice develops
• No clear cause identified after core panel

Refer to asthma specialist if 2:

• Difficulty achieving asthma control
• Step 4 or higher therapy required

• 2 oral steroid bursts in past year or hospitalization for asthma

Common Pitfall to Avoid

Do not simply repeat ALT in 1-3 months without investigation. This outdated approach delays diagnosis and is not cost-effective 1. The most likely causes in your patient are NAFLD (if metabolic risk factors present), medication effect (especially if on zileuton or other hepatotoxic drugs), or viral hepatitis—all of which require specific workup, not just monitoring.