What is the approach to liver function tests (LFTs) in a patient with dengue fever?

Approach to Liver Function Tests in Patients with Dengue Fever

Liver function tests should be monitored regularly in all hospitalized patients with dengue fever, with baseline testing followed by monitoring every 2-3 days throughout the illness, as liver involvement peaks around days 6-7 of illness. 1, 2

Pattern of Liver Involvement in Dengue

• Liver dysfunction is common in dengue infection, with abnormal liver enzymes observed in:

  • AST elevation: 88-93% of patients 3, 4
  • ALT elevation: 73-82% of patients 3, 4
  • GGT elevation: 83% of patients 4
  • Hypoalbuminemia: 57% of patients 3
  • Hyperbilirubinemia: 7-27% of patients 3, 4

• Key characteristic: AST typically rises higher than ALT in dengue infection, which differs from many other forms of viral hepatitis 3, 4

Monitoring Protocol

Initial Assessment

• Obtain baseline liver function tests at admission including:
  • Complete liver profile (ALT, AST, bilirubin, alkaline phosphatase)
  • Serum albumin
  • Prothrombin time/INR
  • Complete blood count with platelets 5

Follow-up Monitoring

• Monitor LFTs every 2-3 days throughout hospitalization 5
• Critical timing: Most significant liver involvement occurs on days 6-7 of illness, so LFTs performed earlier may not reflect the full extent of liver damage 2
• Continue monitoring until normalization of values

Interpretation and Risk Stratification

Severity Classification Based on Aminotransferase Elevation

1. Mild elevation: ≤2-fold increase above upper limit of normal (ULN)
2. Moderate elevation: 3-4 fold increase above ULN
3. Severe elevation: >4-fold increase above ULN 1

Prognostic Significance

• Poor prognostic indicators:

  • AST/ALT >1000 IU/L
  • Significantly elevated bilirubin
  • Decreased albumin levels
  • Prolonged PT/INR 3, 6

• Higher AST and ALT levels correlate with:

  • Greater risk of hemorrhagic complications
  • Higher mortality
  • Longer hospital stays 1, 6

Additional Investigations for Abnormal LFTs

If a dengue patient shows abnormal liver function, additional investigations should include:

1. Serological tests for other causes of hepatitis:

   • Hepatitis B surface antigen
   • Anti-hepatitis C virus antibody 5

2. Imaging studies if clinically indicated:

   • Ultrasound of the liver (to assess for hepatomegaly, which occurs in approximately 34% of pediatric cases) 6
   • Avoid unnecessary imaging to prevent patient transport and potential disease spread 5

3. Consider other causes when liver function continues to deteriorate:

   • Myositis (especially when AST exceeds ALT significantly)
   • Ischemia
   • Cytokine release syndrome
   • Drug-induced liver injury 5

Management Considerations

• Abnormal liver function tests alone are not a contraindication to necessary treatments for dengue fever 5

• For moderate elevations (3-5× ULN):

  • Increase monitoring frequency
  • Investigate other potential causes of liver injury

• For severe elevations (>5× ULN or signs of liver failure):

  • Consider hepatology consultation
  • Monitor for signs of acute liver failure (encephalopathy, coagulopathy)
  • Avoid hepatotoxic medications when possible 5, 7

Pitfalls to Avoid

1. Don't rely on early LFTs alone: Testing only in early illness (days 1-3) may miss significant liver involvement that peaks on days 6-7 2

2. Don't overlook severe liver involvement without plasma leakage: Some patients can develop severe liver injury (AST/ALT >1000 IU/L) without showing other signs of severe dengue 2

3. Don't attribute all LFT abnormalities to dengue alone: Consider concomitant infections and medication effects 5

4. Don't miss the AST>ALT pattern: This characteristic pattern can help differentiate dengue-related liver involvement from other causes of acute hepatitis 3, 4