What is the Fibrosis-4 (FIB-4) test?

From the Guidelines

The FIB-4 test is a valuable non-invasive scoring system for assessing liver fibrosis severity, and a score below 1.3 can reliably exclude advanced fibrosis in patients with NAFLD, with a negative predictive value of ≥90%. The FIB-4 test is calculated using four readily available parameters: age, AST (aspartate aminotransferase), ALT (alanine aminotransferase), and platelet count, with the formula: (Age × AST) ÷ (Platelets × √ALT) 1.

Key Points to Consider

• A FIB-4 score below 1.3 indicates minimal fibrosis and can exclude advanced fibrosis with high negative predictive value 1.
• Patients with FIB-4 score >2.67 are at high risk for advanced fibrosis and should be referred to hepatology for further evaluation 1.
• The FIB-4 test should be interpreted alongside clinical findings and other diagnostic tests for comprehensive liver assessment 1.
• Imaging-based biomarkers, such as vibration-controlled transient elastography (VCTE), shear wave elastography (SWE), and magnetic resonance elastography (MRE), can be used to further assess liver fibrosis severity 1.

Clinical Application

• The FIB-4 test can be used as a first-line point-of-care test to assess liver fibrosis severity in patients with NAFLD 1.
• Patients with indeterminate FIB-4 scores (1.3-2.67) may require additional testing, such as VCTE or MRE, to further assess liver fibrosis severity 1.
• The FIB-4 test can help identify patients who may need more aggressive monitoring or treatment without requiring invasive liver biopsies 1.

Limitations and Future Directions

• The FIB-4 test has limitations, including a modest positive predictive value for confirming advanced fibrosis and the potential for false positive results 1.
• Further research is needed to develop more accurate and reliable non-invasive tests for assessing liver fibrosis severity 1.

From the Research

FIB4 Test Overview

• The FIB4 test is a non-invasive diagnostic tool used to assess liver fibrosis in patients with chronic liver disease 2, 3, 4, 5, 6.
• It is based on four factors: age, aspartate aminotransferase (AST), alanine aminotransferase (ALT) levels, and platelets count.

Diagnostic Accuracy

• The FIB4 test has been shown to be accurate in predicting the absence or presence of advanced fibrosis in patients with viral hepatitis B and C, non-alcoholic fatty liver disease (NAFLD), and alcoholic liver disease (ALD) 2, 3, 6.
• The test has a low-to-moderate accuracy in autoimmune hepatitis 2.
• The FIB4 test can be used to rule out people with at least severe fibrosis (≥ F3) and cirrhosis (F4) in patients with chronic hepatitis C (CHC) 6.

Cut-Off Values

• The cut-off values for the FIB4 test vary depending on the underlying liver disease:
  • Viral hepatitis B: 1.0 and 2.65 2.
  • Viral hepatitis C: 1.45 and 3.25 2, 6.
  • NAFLD: 1.30 (<65 years), 2.0 (≥65 years), and 2.67 2, 3, 5.
  • ALD: low-to-moderate accuracy 2.

Clinical Applications

• The FIB4 test can be used as a screening tool in the primary care setting to identify patients at high risk of liver disease 3, 4.
• It can also be used to predict high-risk varices and long-term survival in hepatocellular carcinoma patients after hepatectomy 2.
• The test may act as a "red flag" for early identification of patients at high risk of advanced liver fibrosis and their referral to specialized care 4.