FIB-4 Calculator
Quantify liver scarring and assess risk for Metabolic Dysfunction-associated Steatotic Liver Disease (MASLD) and Viral Hepatitis using the validated Fibrosis-4 index.
How to Use the Live Calculator ⚡
1. Enter Age
Age dynamically adjusts risk cutoffs.
2. Select Etiology
Choose the primary liver condition.
3. Input Labs
Add AST, ALT, and Platelet values.
4. View Results
Scores update instantly as you type!
Patient Biomarkers
Start typing to see the FIB-4 Score and live clinical interpretation.
🧮 The FIB-4 Formula
The calculation is based on standard clinical units (AST/ALT in U/L, Platelets in 10⁹/L):
📝 Calculation Example
Patient Profile: 55 years old, AST: 45 U/L, ALT: 30 U/L, Platelets: 150 × 10⁹/L.
- Numerator: 55 × 45 = 2,475
- Denominator: 150 × √30 (5.477) = 821.55
- Final FIB-4 Score: 2,475 ÷ 821.55 = 3.01
Interpretation: A score of 3.01 indicates High Risk (> 2.67) for advanced fibrosis.
The Evolution of FIB-4: MASLD & Modern Hepatology
The Fibrosis-4 (FIB-4) index has transitioned from a specialized tool for HIV/HCV co-infection to the primary screening mechanism for Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD). According to the 2024 AASLD Practice Guidelines, the FIB-4 serves as a critical triage tool to determine which patients require advanced imaging, such as Vibration-Controlled Transient Elastography (VCTE/FibroScan).
Why Age 65+ Changes the Calculation
One of the most common errors in clinical practice is applying a static “low-risk” threshold to older populations. Clinical studies have shown that the standard cutoff of 1.30 for MASLD leads to excessive false positives in patients over 65. Modern guidelines now advocate for an age-adjusted cutoff of 2.00 to maintain a high Negative Predictive Value (NPV).
Clinical Comparison: Interpretation Thresholds
| Etiology | Age Group | Low Risk (F0-F1) | High Risk (F3-F4) |
|---|---|---|---|
| MASLD / NAFLD | < 65 Years | < 1.30 | > 2.67 |
| MASLD / NAFLD | ≥ 65 Years | < 2.00 | > 2.67 |
| Chronic HCV | All Ages | < 1.45 | > 3.25 |
Limitations & Clinical Pearls
- Acute Inflammation: Elevated AST/ALT during acute hepatitis can artificially inflate the FIB-4 score.
- Platelet Variability: Conditions like idiopathic thrombocytopenic purpura (ITP) may lead to falsely high fibrosis estimates.
- The Grey Zone: Approximately 30% of patients fall into the “Indeterminate” zone (1.30–2.67), necessitating a second-tier test like the Enhanced Liver Fibrosis (ELF) score or FibroScan.
