FIB-4 Index Calculator
Calculate the FIB-4 index to estimate liver fibrosis stage. FIB-4 = (Age × AST) / (Platelets × √ALT). Score below 1.3 rules out advanced fibrosis; above 2.67 suggests significant fibrosis (F3-F4).
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Why: This page explains what the FIB-4 Index calculator does, what to enter, and how to read the results—without repeating the overview above.
How: Enter your values in the calculator fields below, keep units consistent, then run the calculation to see results and any step-by-step work shown on this page.
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📊 FIB-4 Cutoffs
For informational purposes only — not medical advice. Consult a healthcare professional before acting on results.
FIB-4 estimates liver fibrosis non-invasively using age, AST, ALT, and platelet count. FIB-4 = (Age × AST) / (Platelets × √ALT). Score below 1.3 rules out advanced fibrosis; above 2.67 suggests significant fibrosis (F3-F4). Most accurate in ages 35-65.
Sources: Sterling et al., AASLD/EASL NAFLD guidelines.
Key Takeaways
- • FIB-4 <1.3 excludes advanced fibrosis in ~95% of patients
- • FIB-4 >2.67 suggests F3-F4; hepatology referral recommended
- • Indeterminate zone (1.3-2.67) needs FibroScan or further testing
- • Age <35 or >65: use age-adjusted cutoffs
Did You Know?
How Does FIB-4 Work?
Numerator (Age × AST)
Older age and higher AST increase fibrosis likelihood. AST reflects hepatocyte injury.
Denominator (Platelets × √ALT)
Low platelets (portal hypertension) and √ALT (liver-specific) in denominator lower the score when fibrosis is absent.
Interpretation
Low score = preserved platelets and lower enzymes; high score = thrombocytopenia and elevated AST.
Expert Tips
FIB-4 Risk Categories
| FIB-4 Range | Risk | Action |
|---|---|---|
| <1.3 | Low | Routine follow-up |
| 1.3-2.67 | Indeterminate | FibroScan, hepatology |
| >2.67 | High | Hepatology referral |
Frequently Asked Questions
What is the FIB-4 index?
FIB-4 is a non-invasive score using age, AST, ALT, and platelet count to estimate liver fibrosis. It helps avoid liver biopsy in many patients. Formula: FIB-4 = (Age × AST) / (Platelets × √ALT).
What does FIB-4 < 1.3 mean?
Low probability of advanced fibrosis (F3-F4). Excludes significant fibrosis in ~95% of patients. Routine follow-up is typically sufficient. Age-adjusted cutoffs apply for <35 and >65 years.
When is FIB-4 1.45-3.25 (indeterminate)?
Indeterminate zone. Further evaluation with FibroScan, elastography, or hepatology referral is recommended. ~30-40% of patients fall in this gray zone.
What does FIB-4 > 2.67 mean?
High probability of advanced fibrosis (F3-F4). Strongly consider hepatology referral and further staging. PPV ~65-82% for advanced fibrosis depending on population.
How accurate is FIB-4 by age?
Most accurate in ages 35-65. Age <35 may underestimate fibrosis; age >65 may overestimate. Use age-adjusted cutoffs: <35 use 1.0/2.67; >65 use 2.0/2.67.
Can FIB-4 replace liver biopsy?
FIB-4 is a screening tool. Low scores can rule out advanced fibrosis; high scores suggest it. Indeterminate scores and staging decisions may still require elastography or biopsy.
Key Statistics
Official Data Sources
⚠️ Disclaimer: This calculator is for educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. FIB-4 is a screening tool. Always consult a qualified healthcare provider for liver disease assessment.
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