NAFLD Fibrosis Score (NFS) Calculator
The NAFLD Fibrosis Score (NFS) is a non-invasive scoring system that estimates the probability of advanced liver fibrosis (F3-F4) in patients with non-alcoholic fatty liver disease (NAFLD). It uses age, BMI, diabetes status, AST, ALT, platelet count, and albumin to stratify patients into low, indeterminate, and high risk categories.
About
The NAFLD Fibrosis Score (NFS) was developed and validated by Angulo et al. to predict advanced fibrosis in NAFLD patients. The score ranges from approximately -4 to +4, with lower scores indicating lower probability of advanced fibrosis. It is one of the most validated non-invasive fibrosis markers alongside FIB-4 and APRI.
Formula
NFS = −1.675 + 0.037 × Age + 0.094 × BMI + 1.13 × Diabetes (yes=1) + 0.99 × (AST/ALT) − 0.013 × Platelet (×10⁹/L) − 0.66 × Albumin (g/dL)
A score < −1.455 rules out advanced fibrosis (F0-F2) with high negative predictive value. A score > 0.675 suggests advanced fibrosis (≥F3). Scores between −1.455 and 0.675 are indeterminate, warranting further evaluation with transient elastography (FibroScan) or liver biopsy.
Score Interpretation
NAFLD affects approximately 25% of the global population, with 5-10% having advanced fibrosis. Liver fibrosis is the strongest predictor of liver-related mortality and adverse outcomes in NAFLD patients. Non-invasive scores like NFS and FIB-4 help identify high-risk patients who need hepatology referral, reducing unnecessary liver biopsies while ensuring timely diagnosis of advanced disease.
Low Probability — -100–-1.455
NFS < −1.455 — Advanced fibrosis unlikely (F0-F2).
Management: No fibrosis-specific intervention needed. Manage NAFLD with lifestyle modification.
Indeterminate — -1.455–0.675
NFS −1.455 to 0.675 — Indeterminate risk. Further evaluation needed.
Management: Consider transient elastography (FibroScan) or MRE for fibrosis staging.
High Probability — 0.675+
NFS > 0.675 — Advanced fibrosis likely (≥F3). Refer to hepatology.
Management: Refer to hepatology specialist. Consider FibroScan or liver biopsy. Screen for varices and HCC.
Reference Ranges
| Population | Normal Range | Notes |
|---|---|---|
| Low probability (F0-F2) | < −1.455 | Advanced fibrosis unlikely |
| Indeterminate | −1.455 to 0.675 | Further evaluation indicated |
| High probability (≥F3) | > 0.675 | Advanced fibrosis likely |
Dr. Khaled Hassan
Dr. Khaled is a cardiology consultant with experience in acute cardiac care.
View medical review board & editorial policy →Example Calculation
55-year-old with BMI 32, diabetes, AST 45, ALT 35, platelets 180, albumin 3.8. NFS = −1.675 + (0.037×55) + (0.094×32) + 1.13 + (0.99×1.29) − (0.013×180) − (0.66×3.8) = 0.42. Result: Indeterminate. Recommend FibroScan.
Related Conditions
Common Mistakes
Using NFS in patients without confirmed NAFLD
NFS is validated specifically for NAFLD patients. It should not be used for general populations or other liver diseases.
Frequently Asked Questions
How does NFS compare to FIB-4 for NAFLD staging?
What should I do with an indeterminate NFS?
References
- Angulo P et al. The NAFLD fibrosis score: a noninvasive system that identifies liver fibrosis in patients with NAFLD. Hepatology. 2007;45(4):846-854. PubMed
- Sterling RK et al. Development of a simple noninvasive index to predict significant fibrosis in patients with HIV/HCV coinfection. Hepatology. 2006;43(6):1317-1325. PubMed