How do you interpret a FibroScan (Fibrosis Scan) result?

How to Read and Interpret a FibroScan

FibroScan (transient elastography) is a non-invasive method for assessing liver fibrosis by measuring liver stiffness, with specific cutoff values that reliably identify different stages of fibrosis to guide clinical decision-making. 1

Understanding FibroScan Basics

• FibroScan measures liver stiffness in kilopascals (kPa) by recording the velocity of shear waves across liver parenchyma, with higher values indicating greater fibrosis 2
• For reliable results, a FibroScan procedure should include ≥10 successful measurements with a success rate of at least 60% and an interquartile range less than 30% of the median value 3, 4
• The procedure is quick (approximately 5 minutes), painless, and can be performed in outpatient settings with immediate results 5, 6

Interpreting FibroScan Results by Fibrosis Stage

Standard Cutoff Values for Liver Fibrosis Staging:

• No/Minimal Fibrosis (F0-F1): <8.0 kPa 3
• Significant Fibrosis (≥F2): >7.0 kPa 7, 1
• Advanced Fibrosis (F3): 8-12 kPa 3
• Cirrhosis (F4): >12.5 kPa 3, 7

Diagnostic Performance:

• For significant fibrosis (≥F2), FibroScan has a sensitivity of 75.1% and specificity of 79.3% using cutoffs between 6.0-8.0 kPa 1, 7
• For cirrhosis (F4), FibroScan has a sensitivity of 82.6% and specificity of 89.0% using cutoffs between 11.0-14.0 kPa 1

Clinical Application Algorithm

1. Assess Test Validity:

   • Confirm ≥10 successful measurements 4
   • Verify success rate ≥60% 4
   • Ensure IQR/median ratio <0.30 4

2. Consider Pre-Test Probability:

   • The prevalence of fibrosis in the population significantly impacts interpretation 1
   • In populations with 25% prevalence of significant fibrosis, FibroScan (6.0-8.0 kPa) results in 15.8% false positives and 6.3% false negatives 1
   • In populations with 5% prevalence of cirrhosis, FibroScan (11.0-14.0 kPa) results in 10.5% false positives and 0.9% false negatives 1

3. Apply Disease-Specific Interpretation:

   • For chronic hepatitis B: APRI score >0.5 or FibroScan >7.0 kPa indicates significant fibrosis (≥F2) 1
   • For chronic hepatitis C: Area under ROC curve is 0.79-0.83 for F2, 0.90-0.91 for F3, and 0.91-0.97 for F4 8
   • For NAFLD: Consider using sequential testing with FIB-4 followed by FibroScan 5, 3

4. Make Clinical Decisions Based on Results:

   • Patients with LSM <8.0 kPa: Monitor with repeat surveillance testing in 2-3 years 5, 3
   • Patients with LSM >7.0 kPa (significant fibrosis): Consider treatment initiation for viral hepatitis 7
   • Patients with LSM >12.5 kPa (cirrhosis): Refer to hepatology for management of cirrhosis and screening for complications 5, 7

Important Limitations and Pitfalls

• FibroScan has reduced accuracy in patients with:

  • Ascites (impossible to perform) 1, 3
  • Severe obesity (XL probe may be required) 5, 3
  • Narrow intercostal spaces 1, 3
  • Acute hepatitis (may falsely elevate readings) 1, 3
  • Extrahepatic biliary tract obstruction 1, 3

• False positives can lead to unnecessary treatment, while false negatives may delay needed interventions 1

• Consider using dual cutoffs (low cutoff to rule out, high cutoff to rule in) to improve diagnostic accuracy, though this results in some patients having indeterminate results requiring additional testing 1

• When results are indeterminate or discordant with clinical findings, consider liver biopsy or additional non-invasive tests 1, 3