From the Guidelines
FIB-4 is a reliable non-invasive scoring system for assessing liver fibrosis in patients with non-alcoholic fatty liver disease (NAFLD), with a score less than 1.3 indicating a low risk of advanced fibrosis and a score greater than 2.67 indicating a high risk. The FIB-4 score is calculated using age, AST, ALT, and platelet count, and its diagnostic accuracy for advanced fibrosis is good, with an AUROC of 0.80 1. The score has been shown to correlate with clinical outcomes in patients with NAFLD, and its use as a first-line assessment of liver fibrosis is recommended in primary care 1. Some of the key benefits of FIB-4 include its non-invasive nature, low cost, and ease of use, as it can be calculated using readily available laboratory values 1. However, it is essential to interpret FIB-4 scores in the clinical context, as scores between 1.3 and 2.67 are considered indeterminate and may require additional testing, such as transient elastography (FibroScan) or liver biopsy, for accurate fibrosis staging 1. The use of FIB-4 has been supported by several studies, including a prospective study using serial transient elastography in patients with type 2 diabetes, which found that only 12% of patients had a ≥30% relative increase in liver stiffness after 3 years of follow-up 1. Overall, FIB-4 is a valuable tool for assessing liver fibrosis in patients with NAFLD, and its use can help identify patients at high risk of advanced fibrosis who require further evaluation and management. Key points to consider when using FIB-4 include:
- A score less than 1.3 indicates a low risk of advanced fibrosis
- A score greater than 2.67 indicates a high risk of advanced fibrosis
- Scores between 1.3 and 2.67 are considered indeterminate and may require additional testing
- FIB-4 should be interpreted in the clinical context and combined with other non-invasive tests for improved accuracy 1.
From the Research
FIB-4 Index
- The FIB-4 index is a non-invasive tool used to predict liver fibrosis stage and clinical prognosis in patients with chronic liver disease 2.
- It is calculated based on age, aspartate aminotransferase (AST), and alanine aminotransferase (ALT) levels, and platelets count.
- FIB-4 has been shown to be accurate in predicting the absence or presence of advanced fibrosis in various liver diseases, including viral hepatitis B and C, non-alcoholic fatty liver disease (NAFLD), and alcoholic liver disease (ALD) 2, 3.
Diagnostic Utility of FIB-4
- The diagnostic utility of FIB-4 has been compared to the Scheuer scoring system of liver biopsies in NAFLD patients, showing a sensitivity of 87% and specificity of 87% at cut-off points of 1.45 and 3.25, respectively 3.
- FIB-4 has also been compared to the enhanced liver fibrosis (ELF) test and NAFLD fibrosis score (NFS) in screening for liver fibrosis, showing that a sequential test strategy of FIB-4 followed by ELF can reduce futile referrals and improve diagnostic accuracy 4.
- However, FIB-4 has been shown to have low accuracy for screening for liver fibrosis in low-prevalence populations, with a high risk of overdiagnosis and false-negatives 5.
Cut-off Points for FIB-4
- Different cut-off points have been proposed for FIB-4, including 1.0 and 2.65 for viral hepatitis B, 1.45 and 3.25 for viral hepatitis C, and 1.30 and 2.67 for NAFLD 2.
- A study has also proposed new cut-off points for FIB-4 and NFS to guide sequential non-invasive assessment of liver fibrosis by magnetic resonance elastography in NAFLD, with cut-off points of 1.505 for FIB-4 and -0.835 for NFS 6.
Clinical Applications of FIB-4
- FIB-4 may be used as a screening tool in the primary care setting to identify patients at risk of liver fibrosis 3.
- It can also be used to predict high-risk varices and long-term survival in hepatocellular carcinoma patients after hepatectomy 2.
- Additionally, FIB-4 has been shown to have predictive value for mechanical ventilation and 30-day mortality in acute liver injury caused by COVID-19 2.