FIB-4 and APRI Calculator: Liver Fibrosis Indices
FIB-4 (Sterling 2006) uses age, AST, ALT and platelets. AASLD 2023 thresholds concern the likelihood of advanced fibrosis in metabolic fatty liver disease, not fibrosis staging. Ages 35–65: lower threshold 1.3; over 65: 2.0; upper threshold 2.67. No category is assigned below 35; do not interpret during acute illness. APRI (Wai 2003) and thresholds 0.5/1.5 concern significant fibrosis in chronic hepatitis C and do not automatically transfer to other diseases.
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Calculation
Result
- FIB-4
- 1.27 index
- Interpretation
- Below the assessment threshold: a low result does not exclude all liver disease
- APRI
- 0.45 · significant fibrosis unlikely index
Low risk < 1.3; gray zone up to 2.67; high risk > 2.67
Thresholds of 0.5 and 1.5 concern significant fibrosis in chronic hepatitis C; they do not assign a fibrosis stage.
FIB-4 (Sterling 2006) uses age, AST, ALT and platelets. AASLD 2023 thresholds concern the likelihood of advanced fibrosis in metabolic fatty liver disease, not fibrosis staging. Ages 35–65: lower threshold 1.3; over 65: 2.0; upper threshold 2.67. No category is assigned below 35; do not interpret during acute illness. APRI (Wai 2003) and thresholds 0.5/1.5 concern significant fibrosis in chronic hepatitis C and do not automatically transfer to other diseases. Reference ranges are population benchmarks from the cited sources. Laboratories use their own ranges, and interpretation depends on clinical context: discuss the result with your physician.
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How it is calculated
FIB-4 (Sterling 2006) uses age, AST, ALT and platelets. AASLD 2023 thresholds concern the likelihood of advanced fibrosis in metabolic fatty liver disease, not fibrosis staging. Ages 35–65: lower threshold 1.3; over 65: 2.0; upper threshold 2.67. No category is assigned below 35; do not interpret during acute illness. APRI (Wai 2003) and thresholds 0.5/1.5 concern significant fibrosis in chronic hepatitis C and do not automatically transfer to other diseases.
Formula
FIB-4 = age × AST / (platelets × √ALT); APRI = (AST / AST_ULN) × 100 / platelets. FIB-4 (Sterling 2006) uses age, AST, ALT and platelets. AASLD 2023 thresholds concern the likelihood of advanced fibrosis in metabolic fatty liver disease, not fibrosis staging. Ages 35–65: lower threshold 1.3; over 65: 2.0; upper threshold 2.67. No category is assigned below 35; do not interpret during acute illness. APRI (Wai 2003) and thresholds 0.5/1.5 concern significant fibrosis in chronic hepatitis C and do not automatically transfer to other diseases.
Limits of the method
FIB-4 helps estimate the likelihood of advanced fibrosis but cannot confirm or exclude it in every individual. Accuracy is low below age 35; do not interpret it during acute illness. Non-liver causes of low platelets and muscle-related AST elevation can distort the result. Thresholds depend on age, disease cause and clinical context.
Sources of the method
- Rinella M.E. et al. AASLD Practice Guidance on the clinical assessment and management of nonalcoholic fatty liver disease. Hepatology, 2023.
- Sterling RK et al. Development of a simple noninvasive index to predict significant fibrosis in patients with HIV/HCV coinfection. Hepatology, 2006
- Wai CT et al. A simple noninvasive index can predict both significant fibrosis and cirrhosis in patients with chronic hepatitis C. Hepatology, 2003
- European Association for the Study of the Liver. et al. EASL Clinical Practice Guidelines on non-invasive tests for evaluation of liver disease severity and prognosis - 2021 update. J Hepatol, 2021
This calculation is for reference only and is not medical advice, a diagnosis or a prescription. If you have a medical condition, are pregnant, take medication or have any doubts, discuss the result with a physician or a qualified nutrition professional.
How to use the calculation
Enter the starting values
FIB-4 (Sterling 2006) uses age, AST, ALT and platelets. AASLD 2023 thresholds concern the likelihood of advanced fibrosis in metabolic fatty liver disease, not fibrosis staging. Ages 35–65: lower threshold 1.3; over 65: 2.0; upper threshold 2.67. No category is assigned below 35; do not interpret during acute illness. APRI (Wai 2003) and thresholds 0.5/1.5 concern significant fibrosis in chronic hepatitis C and do not automatically transfer to other diseases.
Adjust the parameters
FIB-4 = age × AST / (platelets × √ALT); APRI = (AST / AST_ULN) × 100 / platelets. FIB-4 (Sterling 2006) uses age, AST, ALT and platelets. AASLD 2023 thresholds concern the likelihood of advanced fibrosis in metabolic fatty liver disease, not fibrosis staging. Ages 35–65: lower threshold 1.3; over 65: 2.0; upper threshold 2.67. No category is assigned below 35; do not interpret during acute illness. APRI (Wai 2003) and thresholds 0.5/1.5 concern significant fibrosis in chronic hepatitis C and do not automatically transfer to other diseases.
Read the result
FIB-4 helps estimate the likelihood of advanced fibrosis but cannot confirm or exclude it in every individual. Accuracy is low below age 35; do not interpret it during acute illness. Non-liver causes of low platelets and muscle-related AST elevation can distort the result. Thresholds depend on age, disease cause and clinical context.
Frequently asked questions
What does the calculation show?
FIB-4 (Sterling 2006) uses age, AST, ALT and platelets. AASLD 2023 thresholds concern the likelihood of advanced fibrosis in metabolic fatty liver disease, not fibrosis staging. Ages 35–65: lower threshold 1.3; over 65: 2.0; upper threshold 2.67. No category is assigned below 35; do not interpret during acute illness. APRI (Wai 2003) and thresholds 0.5/1.5 concern significant fibrosis in chronic hepatitis C and do not automatically transfer to other diseases.
What limitations apply?
FIB-4 helps estimate the likelihood of advanced fibrosis but cannot confirm or exclude it in every individual. Accuracy is low below age 35; do not interpret it during acute illness. Non-liver causes of low platelets and muscle-related AST elevation can distort the result. Thresholds depend on age, disease cause and clinical context.
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What next
Formula breakdowns, biomarker reference ranges and nutrition articles with cited sources are in the NutriFit knowledge base.
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