FIB-4 Calculator
Calculate the FIB-4 score and fibrosis risk category based on age, AST, ALT, and platelet count. FIB-4 Calculator helps clinicians and adults with liver concerns estimate fibrosis risk and guide appropriate medical follow-up.
Highlights
- Estimates liver fibrosis risk using the validated FIB-4 score.
- Uses age, AST, ALT, and platelet count for calculation.
- Provides a clear low, indeterminate, or high-risk category.
- Supports platelet counts in multiple common units.
- Helps guide appropriate medical follow-up for liver concerns.
Table of Contents
How FIB-4 Calculator Works?
The FIB-4 Calculator estimates the likelihood of significant liver fibrosis using four routine clinical variables: age, aspartate aminotransferase (AST), alanine aminotransferase (ALT), and platelet count. The score is calculated by multiplying age by AST, then dividing by platelet count multiplied by the square root of ALT.
Higher FIB-4 scores generally indicate a greater probability of advanced liver fibrosis, while lower scores make advanced fibrosis less likely. The calculator accepts adults aged 18 to 120 years, AST and ALT values from 1 to 1,000 U/L, and platelet counts from 10 to 1,000 in the supported platelet-count format.
| FIB-4 score | Typical interpretation |
|---|---|
| Below 1.3 | Low estimated risk of advanced fibrosis in many adults |
| 1.3 to 2.67 | Indeterminate risk; additional clinical assessment may be appropriate |
| Above 2.67 | High estimated risk; further evaluation for advanced fibrosis is commonly considered |
For adults older than 65 years, age-adjusted interpretation is often used: a score below 2.0 is commonly considered low risk, 2.0 to 2.67 indeterminate, and above 2.67 high risk. The displayed score is an estimate to support clinical follow-up, not a diagnosis of liver fibrosis.
Practical Use Cases
Primary care clinicians: A clinician can use the FIB-4 score during assessment of abnormal liver tests, metabolic risk factors, or suspected fatty liver disease to identify adults who may need repeat testing or additional liver evaluation.
Hepatology and gastroenterology teams: Specialists can use the score as an initial, non-invasive risk-stratification measure alongside the patient's history, examination, imaging, and other fibrosis assessments.
Adults monitoring liver health: People who have access to recent age, AST, ALT, and platelet results can use the calculator to understand why their results may warrant discussion with a healthcare professional, without treating the estimate as a definitive diagnosis.
Clinical researchers and educators: Researchers and students can apply the formula to example laboratory profiles to demonstrate how age, enzyme levels, and platelet count influence an estimated fibrosis-risk category.
Accuracy and Limitations
The FIB-4 score is a validated screening and risk-stratification tool, but it cannot directly measure liver fibrosis or replace specialist assessment. Results may be misleading during acute hepatitis, temporary AST or ALT elevations, alcohol-related injury, muscle injury, or conditions that independently reduce platelet count. Age can substantially influence the result, particularly in older adults, so age-adjusted thresholds are commonly applied after age 65. A high or indeterminate score should be interpreted with the patient's history and may require additional testing, while a low score does not completely exclude clinically important liver disease.
Quick Examples
Example #1: Low-Risk Screening Profile
Example of an adult with routine liver results associated with a lower estimated risk of advanced fibrosis.
Example #2: Intermediate-Risk Profile
Example of an adult whose laboratory results may produce an indeterminate FIB-4 fibrosis risk assessment.
Example #3: Higher-Risk Screening Profile
Example of an older adult with elevated AST and reduced platelet count, supporting evaluation for higher fibrosis risk.
