About the NAFLD Fibrosis Score
The NAFLD Fibrosis Score (NFS) is a non-invasive scoring system developed by Angulo and colleagues to estimate the probability of advanced liver fibrosis (stage F3-F4) in people with non-alcoholic fatty liver disease. It uses six routinely available variables — age, body mass index, diabetes or impaired fasting glucose status, the AST/ALT ratio, platelet count, and serum albumin — to produce a single continuous score, avoiding the need for a liver biopsy in many patients.
How the score is calculated
NFS = -1.675 + (0.037 x age in years) + (0.094 x BMI in kg/m²) + (1.13 x diabetes/IFG, scored 1 if present or 0 if absent) + (0.99 x AST/ALT ratio) - (0.013 x platelet count in x10^9/L) - (0.66 x albumin in g/dL).
Interpreting the result
- A score below -1.455 indicates a low probability of advanced (F3-F4) fibrosis, with a high negative predictive value in validation studies.
- A score above 0.676 indicates a high probability of advanced fibrosis and often prompts referral for further hepatology evaluation.
- Scores between -1.455 and 0.676 fall in an indeterminate zone, where additional testing such as transient elastography (FibroScan), other non-invasive markers, or liver biopsy may be needed to clarify fibrosis stage.
Limitations
The NFS was derived and validated in adults with biopsy-confirmed NAFLD and is not intended for other liver diseases. Extremes of age or BMI, recent acute illness, and conditions affecting albumin or platelet counts independent of liver disease can all shift the score. It estimates probability, not certainty, and roughly a quarter of patients fall in the indeterminate range.
When to consult a professional
This calculator performs the standard NFS arithmetic for education and screening triage. It is not a diagnosis. Any decision about further imaging, elastography, biopsy, or treatment should be made with a qualified healthcare provider who can review the full clinical picture.