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🧬 HEPATOLOGY · MASLD · METABOLIC

NAFLD Fibrosis Score Calculator (NFS)

Non-invasive detection of advanced liver fibrosis (F3–F4) in NAFLD/MASLD using Age, BMI, Diabetes status, AST/ALT ratio, Platelets, and Albumin. Validated by Angulo et al. 2007 (AUROC 0.88, NPV 93%, PPV 90%).

Angulo 2007AASLD / EASL AlignedMETAVIR F0–F4
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NAFLD Fibrosis Score (NFS)

Clinical & Laboratory Fibrosis Stratification

MASLD
Impaired fasting glucose (100–125 mg/dL) or Type 2 DM
kg/m²
Or Auto-Calculate from Height & Weight:
cm
kg
Enter height & weight to auto-calculate BMI, or type BMI directly above.
U/L
Normal: 10–40 U/L
U/L
Normal: 7–56 U/L
Calculated AST / ALT Ratio:—
×10⁹/L
Normal: 150–400 ×10⁹/L
g/dL
Normal: 3.5–5.0 g/dL (if g/L, divide by 10)

Mathematical Formula (Angulo et al., 2007)

NFS = −1.675 + (0.037 × Age) + (0.094 × BMI) + (1.13 × IFG/DM [1 or 0]) + (0.99 × AST/ALT) − (0.013 × Platelets) − (0.66 × Albumin)
Cutoffs: Low Risk < −1.455 (F0–F2) · Indeterminate −1.455 to 0.675 · High Risk > 0.675 (F3–F4) · AUROC = 0.88.
📋 Contents — tap to expand
1. NFS Score Interpretation2. Variables & Rationale3. MASLD & Clinical Impact4. NFS vs. FIB-4 Algorithm5. Frequently Asked Questions
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Reviewed by Dr. Sharma, MBBS AFIH

Medical Officer, AAC Clinic · Updated 2026-09-05

1NFS Score Interpretation & Clinical Action

NFS ScoreRisk TierFibrosis StageDiagnostic AccuracyRecommended Clinical Action
< −1.455Low RiskF0–F2 (Mild / None)NPV 93%Advanced fibrosis unlikely. Defer liver biopsy. Optimize metabolic risk factors. Re-screen in 1–2 years.
−1.455 to 0.675IndeterminateF1–F3 (Variable)—Inconclusive. Escalate to secondary testing: Vibration-Controlled Transient Elastography (FibroScan) or MRE.
> 0.675High RiskF3–F4 (Advanced / Cirrhosis)PPV 90%High probability of advanced fibrosis. Urgent hepatology referral. Confirm with elastography/biopsy. Initiate HCC surveillance.
⚠️ The Indeterminate Zone in Clinical Practice: Between 25% and 35% of all MASLD patients fall into the indeterminate window (−1.455 to 0.675). This reflects genuine biological transition and should trigger second-line non-invasive testing (such as FibroScan / liver stiffness measurement) rather than clinical dismissal.

2NFS Variables & Physiological Rationale

VariableModel CoefficientUnitPhysiological & Pathological Rationale
Intercept Constant−1.675—Baseline mathematical regression offset.
Age+0.037yearsCumulative duration of metabolic insult; older individuals demonstrate higher fibrosis density.
BMI+0.094kg/m²Adiposity drives lipotoxicity, systemic inflammation, and hepatic stellate cell activation.
IFG / Diabetes+1.1301 or 0The strongest independent predictor (+1.13); hyperinsulinemia directly accelerates hepatic fibrogenesis.
AST / ALT Ratio+0.990ratioProgressive fibrosis impairs sinusoidal clearance of AST, shifting the ratio >1.0 (De Ritis ratio).
Platelet Count−0.013×10⁹/LAdvancing fibrosis induces portal hypertension, leading to splenic sequestration and lower platelets.
Serum Albumin−0.660g/dLDecreasing albumin reflects impaired hepatic synthetic reserve in advanced bridging fibrosis or cirrhosis.

3From NAFLD to MASLD — Clinical Context

In 2023, multinational liver societies (AASLD, EASL, ALEH) finalized the Delphi consensus updating Non-Alcoholic Fatty Liver Disease (NAFLD) to Metabolic dysfunction-Associated Steatotic Liver Disease (MASLD). MASLD encompasses the spectrum from simple hepatic steatosis to Metabolic dysfunction-Associated Steatohepatitis (MASH) and progressive cirrhosis.

The primary driver of all-cause and liver-related mortality in MASLD is the presence of advanced fibrosis (F3–F4), not the absolute percentage of liver fat. Identifying advanced fibrosis non-invasively allows clinicians to triage patients for hepatocellular carcinoma (HCC) ultrasound screening and esophageal variceal surveillance.

4NFS vs. FIB-4 Sequential Pathway

EASL 2024 Sequential Triaging Algorithm

1. First-Line Screen: Calculate FIB-4 on all patients with fatty liver (Age, AST, ALT, Platelets).

2. FIB-4 < 1.30: Low risk → Primary care lifestyle management; recheck in 2 years.

3. FIB-4 Indeterminate (1.30–2.67): Calculate NFS or proceed directly to FibroScan for second-line stratification.

4. FIB-4 > 2.67 or NFS > 0.675: High risk → Direct hepatology referral for elastography confirmation or biopsy.

5Frequently Asked Questions

What is the NAFLD Fibrosis Score (NFS)?+
The NAFLD Fibrosis Score is an internationally validated clinical algorithm that estimates the likelihood of advanced hepatic fibrosis (METAVIR F3–F4) in MASLD patients using six routine parameters: Age, BMI, Diabetes/IFG, AST/ALT ratio, Platelets, and Albumin.
What does IFG or Diabetes mean in the formula?+
Score as 1 (Yes) if the patient has impaired fasting glucose (fasting glucose 100–125 mg/dL), prediabetes (HbA1c 5.7%–6.4%), or established Type 2 Diabetes Mellitus. Score 0 (No) only if glycemic markers are strictly normal with no diabetes history.
When is the NAFLD Fibrosis Score inaccurate?+
The score is inaccurate in acute hepatitis (transaminases reflect necrosis, not fibrosis), non-hepatic thrombocytopenia (ITP, hematologic disorders), significant concurrent alcohol consumption (>14–21 units/week), and malnutrition-induced hypoalbuminemia.
Clinical Disclaimer: The NAFLD Fibrosis Score is a probabilistic triage tool intended for qualified healthcare providers. It does not replace clinical evaluation or liver histology. Correlate scores with transient elastography (FibroScan) or magnetic resonance elastography before initiating cirrhosis management or invasive interventions.