FIB-4 Index Calculator
Estimate the risk of advanced liver fibrosis using age, AST, ALT and platelet count. Designed primarily for adults with suspected or known chronic liver disease.
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What is the FIB-4 Index?
The FIB-4 Index is a non-invasive fibrosis assessment score calculated from four routinely available variables: age, AST, ALT and platelet count.
It is commonly used as an initial risk-stratification tool for advanced liver fibrosis, particularly in patients with metabolic dysfunction-associated steatotic liver disease (MASLD), chronic viral hepatitis and other chronic liver conditions.
A low FIB-4 can help identify patients who are less likely to have advanced fibrosis, whereas an elevated result may indicate the need for further non-invasive assessment.
FIB-4 Formula
Age: years
AST: U/L
ALT: U/L
Platelet count: ×10⁹/L
FIB-4 Interpretation
| FIB-4 | Risk Category | General Interpretation |
|---|---|---|
| <1.30 | Low risk | Advanced fibrosis is less likely. |
| 1.30–2.67 | Indeterminate | Further fibrosis assessment may be appropriate. |
| >2.67 | High risk | Advanced fibrosis is more likely and further evaluation should be considered. |
Important: In adults older than 65 years, a higher cutoff around 2.0 is commonly considered because the standard 1.30 cutoff has reduced specificity in this age group.
How to Use the FIB-4 Calculator
- Enter the patient's age in years.
- Enter AST (SGOT) in U/L.
- Enter ALT (SGPT) in U/L.
- Enter platelet count in ×10⁹/L.
- Click Calculate FIB-4.
Clinical Considerations
- FIB-4 is a risk-stratification tool, not a direct measurement of liver fibrosis.
- Acute liver injury can substantially affect AST and ALT and may make the score less representative of chronic fibrosis risk.
- Thrombocytopenia may occur for causes unrelated to hepatic fibrosis and can increase the FIB-4 score.
- An indeterminate or elevated FIB-4 does not by itself establish advanced fibrosis or cirrhosis.
- Additional assessment may include transient elastography or another validated non-invasive fibrosis test, depending on the clinical setting.
FIB-4 Calculator – Frequently Asked Questions
What does the FIB-4 score measure?
FIB-4 estimates the likelihood of advanced liver fibrosis using age, AST, ALT and platelet count. It does not directly measure liver fibrosis.
What is a low FIB-4 score?
In adults younger than 65 years, a FIB-4 below 1.30 is commonly considered low risk for advanced fibrosis.
What does FIB-4 above 2.67 mean?
A value above 2.67 is associated with a higher likelihood of advanced fibrosis and generally warrants further clinical assessment.
Why is age important in FIB-4?
Age is part of the FIB-4 equation. In older adults, particularly those over 65 years, the standard low-risk cutoff has reduced specificity.
Can FIB-4 diagnose cirrhosis?
No. FIB-4 cannot independently diagnose cirrhosis. It is a screening and risk-stratification tool and should be interpreted with other clinical and non-invasive assessments.
Can FIB-4 be used during acute hepatitis?
FIB-4 may be less reliable when AST or ALT is markedly elevated because acute hepatocellular injury can influence the calculated score.
What should be done after a high FIB-4?
The result should be interpreted in clinical context. Further non-invasive fibrosis assessment, such as elastography, may be appropriate depending on the patient's underlying liver disease and risk factors.
Can a normal FIB-4 completely exclude liver disease?
No. A low FIB-4 primarily indicates a lower likelihood of advanced fibrosis. It does not exclude steatosis, inflammation or other liver disease.
Medical Disclaimer: This calculator is intended for educational and clinical reference purposes. FIB-4 is an estimate of fibrosis risk and should not be interpreted as a direct measurement of liver fibrosis or a definitive diagnosis of cirrhosis. Results should be interpreted together with the patient's clinical history, liver biochemistry, platelet count, imaging and other appropriate investigations. This calculator does not replace professional medical evaluation.
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