What is the Fib-4 (Fibrosis-4) index?

From the Guidelines

FIB-4 is a valuable non-invasive scoring system for assessing liver fibrosis in patients with non-alcoholic fatty liver disease (NAFLD), and a score below 1.3 suggests minimal fibrosis with high negative predictive value, while a score above 3.25 indicates advanced fibrosis with high positive predictive value, as recommended by the most recent guidelines 1. To calculate FIB-4, you need four parameters: age, AST (aspartate aminotransferase), ALT (alanine aminotransferase), and platelet count. The formula is: Age (years) × AST (U/L) / [Platelet count (10^9/L) × √ALT (U/L)]. Some key points to consider when using FIB-4 include:

• A FIB-4 score below 1.3 suggests minimal fibrosis with high negative predictive value, and patients with this score can be reassessed every 2 years 1.
• A FIB-4 score above 3.25 indicates advanced fibrosis with high positive predictive value, and patients with this score should be referred to a hepatologist for further evaluation and management 1.
• Scores between 1.3 and 3.25 are indeterminate and may require additional testing like elastography or liver biopsy 1.
• FIB-4 is valuable because it uses readily available laboratory tests to help clinicians assess liver fibrosis severity without invasive procedures, allowing for better disease monitoring and treatment decisions 1.
• However, FIB-4 should be interpreted in the clinical context as it may be less accurate in certain populations like the elderly or those with specific comorbidities 1. It's also important to note that the diagnostic performance of FIB-4 for advanced fibrosis may be lower in patients with NAFLD and T2DM, and patients aged ≥65 years with FIB-4 <2.0 are not considered high-risk 1. Overall, FIB-4 is a useful tool for assessing liver fibrosis in patients with NAFLD, and its use can help guide clinical decision-making and improve patient outcomes, as supported by the most recent and highest quality studies 1.

From the Research

Definition and Purpose of FIB-4

• FIB-4 is a noninvasive scoring test used to assess liver fibrosis risk in patients with chronic liver disease 2.
• The test is simple, free of charge, and can be automatically generated, allowing for earlier recognition of liver disease in the general population 2.

Association with Liver Fibrosis

• FIB-4 scores are associated with the incidence of severe liver outcomes, including cirrhosis, hepatocellular carcinoma, and liver transplantation 3.
• Advanced fibrosis, as indicated by high FIB-4 scores, is associated with a higher risk of severe liver disease outcomes 3.
• A significant relationship was observed between FIB-4 fibrosis risk stages and other fibrosis markers, such as the NAFLD Fibrosis Score (NFS) and Fibrometer (FM) 2.

Comparison with Other Fibrosis Markers

• FIB-4 scores were compared to NFS and FM scores in a study of primary care patients without known liver disease, and significant relationships were observed between the three markers 2.
• The prevalence of significant liver fibrosis by FIB-4 was 19.1%, compared to 16.8% by NFS and 8.2% by FM 2.

Use in Clinical Practice

• FIB-4 scores can be used to identify patients at risk of liver fibrosis and to monitor disease progression 2, 3.
• The test can be used in primary care settings to screen for liver disease in patients without known liver pathology 2.
• FIB-4 scores can also be used to assess the efficacy of treatments, such as ledipasvir/sofosbuvir, in patients with chronic hepatitis C 4, 5, 6.