Medical Term for Elevated Liver Stiffness Test (LST)
The medical term for elevated liver stiffness measurement (LSM) is hepatic fibrosis, with higher values indicating more advanced stages of fibrosis progressing to cirrhosis. 1
Understanding Liver Stiffness Measurement
Liver stiffness measurement (LSM) is a non-invasive technique primarily used to assess the degree of liver fibrosis. The most common method to measure liver stiffness is transient elastography (TE), commercially known as FibroScan. This technique:
- Measures the velocity of a shear wave through liver tissue
- Reports results in kilopascals (kPa)
- Higher values indicate stiffer liver tissue, correlating with more advanced fibrosis
Interpretation of Liver Stiffness Values
The European Association for the Study of the Liver (EASL) provides the following general interpretation framework 1, 2:
| Liver Stiffness (kPa) | Interpretation |
|---|---|
| <8 kPa | Low risk of advanced fibrosis |
| 8-12 kPa | Indeterminate risk zone |
| >12 kPa | High risk of advanced fibrosis |
| ≥15 kPa | Highly suggestive of compensated advanced chronic liver disease |
| >16 kPa | Possible cirrhosis (requires referral to hepatology) |
Factors Affecting Liver Stiffness Measurements
It's important to note that several factors can cause falsely elevated liver stiffness values, independent of fibrosis 1:
- Acute inflammation/hepatitis: Can significantly increase LSM values (1.3-3 fold increase during ALT flares)
- Cholestasis: Bile duct obstruction increases liver stiffness
- Alcohol consumption: Recent alcohol intake can elevate measurements
- Heart failure: Central venous pressure directly influences liver stiffness 3
- Food intake: Recent meals can temporarily increase measurements
- Body mass index (BMI): Both very low BMI (<18.5) and obesity can affect readings 4
Clinical Applications
Liver stiffness measurement has several important clinical applications:
- Fibrosis staging: Primary use is to non-invasively assess the stage of liver fibrosis
- Portal hypertension assessment: LSM correlates with hepatic venous pressure gradient (HVPG) and can predict clinically significant portal hypertension 5
- Monitoring disease progression: Serial measurements can track fibrosis progression or regression
- Reducing need for liver biopsy: High accuracy for detecting advanced fibrosis (≥F3) 1
Improving Accuracy
To improve diagnostic accuracy:
- Repeat measurements: Performing two LSM tests within a short period can reduce false positives and unnecessary liver biopsies 6
- Context interpretation: Always interpret results in the context of clinical, laboratory, and imaging findings 1
- Consider confounding factors: Assess for conditions that may artificially elevate readings
Disease-Specific Considerations
The prevalence of elevated liver stiffness varies by underlying condition:
- Alcohol-related liver disease: Higher cut-off values may be needed (34.9 kPa for significant portal hypertension) 5
- Viral hepatitis: Lower cut-off values (20.5 kPa for significant portal hypertension in HCV) 5
- Diabetes: Elevated liver stiffness is found in approximately 5.2% of patients with type 1 diabetes and 19.8% of patients with type 2 diabetes 7
Important Caveats
- LSM should not be performed in patients with AST serum levels >100 U/L due to risk of falsely elevated readings 1
- Inflammation, cholestasis, or liver congestion may interfere with LSM, independently of fibrosis 1
- Heart failure can dramatically increase liver stiffness (up to 75 kPa), which reverses upon treatment 3
In clinical practice, elevated liver stiffness should prompt further evaluation for the underlying cause of liver disease and consideration of appropriate management strategies based on the degree of fibrosis detected.