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Non-invasive score used to estimate advanced fibrosis in patients with NAFLD/MASLD.
Clinical decision-support tool for qualified healthcare professionals. Results are not a diagnosis and should not replace professional clinical judgment.
The NAFLD Fibrosis Score helps identify patients at low or high risk of advanced fibrosis without liver biopsy.
Specialty
GastroenterologyCategory
GastroenterologyDifficulty
Basic
Estimated Time
30 seconds
Version
1.0
Last Updated
2026-07
Formula
Keywords
| Classification | Range |
|---|---|
Low Probability | < -1.455 |
Indeterminate | -1.455 to 0.676 |
High Probability | > 0.676 |
Calculates the NAFLD Fibrosis Score to estimate the probability of advanced fibrosis non-invasively in patients with NAFLD/MASLD.
NAFLD fibrosis score = -1.675 + (0.037 x age) + (0.094 x BMI) + (1.13 x diabetes) + (0.99 x AST/ALT) - (0.013 x platelets) - (0.66 x albumin), with age in years, BMI in kg/m2, diabetes coded 0 or 1, platelets in x10^9/L, and albumin in g/dL.
Age in years, multiplied by 0.037.
Body mass index in kg/m2, multiplied by 0.094.
Presence of diabetes or impaired fasting glucose, coded 1 if present and 0 if absent.
Aspartate aminotransferase in U/L, used as the numerator of the AST/ALT ratio.
Alanine aminotransferase in U/L, used as the denominator of the AST/ALT ratio.
Platelet count in x10^9/L, multiplied by -0.013.
Serum albumin in g/dL, multiplied by -0.66.
NFS <−1.455 indicates low probability of advanced fibrosis; −1.455 to 0.676 is indeterminate; >0.676 indicates high probability of advanced fibrosis.
The NAFLD Fibrosis Score is an AASLD-endorsed, non-invasive tool that helps identify patients with NAFLD/MASLD at risk of advanced fibrosis, reducing unnecessary biopsies.
A 58-year-old man with MASLD and type 2 diabetes has BMI 32 kg/m², AST 60 U/L, ALT 40 U/L, platelets 180 ×10⁹/L, and albumin 3.8 g/dL.
Inputs:
Expected Result: NFS = −1.675 + 0.037(58) + 0.094(32) + 1.13(1) + 0.99(60/40) − 0.013(180) − 0.66(3.8) ≈ 1.246 — high probability of advanced fibrosis (>0.676).
The NAFLD fibrosis score adds BMI, diabetes or impaired fasting glucose, and albumin to age, the AST/ALT ratio, and platelets, and it was built and validated specifically in NAFLD cohorts. FIB-4 uses age, AST, ALT, and platelets without metabolic variables. Both estimate advanced fibrosis non-invasively, both have an indeterminate middle range, and neither replaces elastography or biopsy when staging is required.
An indeterminate result between -1.455 and 0.676 does not resolve the question of advanced fibrosis. Guidance directs these patients to further evaluation, typically elastography and occasionally biopsy, rather than relying on the score alone. Only results below -1.455, indicating low probability, or above 0.676, indicating high probability, are used to triage without further testing.
The formula uses the ratio of AST to ALT as one of its terms, along with separate coefficients for the other variables, so both raw enzyme values in U/L are required. Entering a pre-calculated ratio or swapping the two values changes that term and moves the score relative to the -1.455 and 0.676 cutoffs.
Disclaimer: This calculator is intended for educational and clinical decision support purposes only. The NAFLD Fibrosis Score is a screening tool and does not replace clinical evaluation or confirmatory fibrosis testing.