NFS fibrosis score
NFS (NAFLD Fibrosis Score) is a non-invasive score that identifies people at high risk of NAFLD progressing to advanced fibrosis and cirrhosis. It is calculated from age, BMI, the presence of diabetes and three routine blood tests — and assigns the result to a risk zone right away.
What NFS is and why it matters
NFS (NAFLD Fibrosis Score) is a calculated index designed to identify the group of patients at high risk of NAFLD (non-alcoholic fatty liver disease) transforming into fibrosis and/or cirrhosis. It requires no equipment: all you need is age, height and weight (for BMI), information about diabetes and routine blood tests.
Non-alcoholic (metabolic-associated) fatty liver disease (NAFLD/MAFLD) is a chronic liver disease linked to metabolic dysfunction, in which macrovesicular steatosis is found in more than 5% of hepatocytes.
Fibrosis and cirrhosis in NAFLD
Liver fibrosis is the gradual replacement of healthy liver tissue with connective tissue, which disrupts the organ's structure and function. Its extreme stage is cirrhosis: a chronic disease in which the liver parenchyma is irreversibly replaced by fibrous connective tissue (stroma). If steatosis indices answer the question “is there fat,” NFS answers the next one: “has the process progressed to advanced scarring.”
What you need for the calculation
NFS is calculated from six factors — two about you and four from lab tests:
- Age, in years. It enters the calculation directly.
- BMI. The calculator works it out from your height and weight (BMI = weight / height²).
- Impaired fasting glucose or diabetes. A binary “yes/no” factor — a meaningful marker of NAFLD progression.
- AST and ALT, U/L. The formula uses their AST/ALT ratio, which rises as fibrosis develops.
- Platelets, ×10⁹/L. As fibrosis progresses, their count usually falls.
- Albumin, g/L. A protein synthesized by the liver; it declines with significant damage.
How to prepare correctly
Height and weight
Accuracy depends on your measurement technique. Measure height without shoes; measure weight under the same conditions, ideally in the morning, on an empty stomach and on the same scale.
Blood tests
AST, ALT and albumin are drawn on an empty stomach; platelets come from a complete (clinical) blood count in units of ×10⁹/L. The day before, avoid intense workouts and alcohol — they temporarily distort the enzymes.
NFS calculator
Enter your age, height, weight, diabetes status and lab results — the calculator will work out your BMI, compute the NFS index, and determine the risk zone and fibrosis stage. The calculation runs on the server.
Thresholds (Angulo, 2007): < −1.455 — F0–F2 · from −1.455 to 0.675 — “gray zone” · > 0.675 — F3–F4.
How to read the result
NFS has two threshold points that split the result into three zones:
| NFS | Stage | Interpretation |
|---|---|---|
| < −1.455 | F0–F2 | Low probability of fibrosis |
| −1.455 … 0.675 | — | Indeterminate score, “gray zone” |
| > 0.675 | F3–F4 | High probability of fibrosis |
F0–F2. Advanced fibrosis is unlikely. Monitoring and work on risk factors.
No definitive conclusion is possible — further work-up is needed (elastometry/ELF).
F3–F4. A high risk of advanced fibrosis; confirmation and a management plan are essential.
Why these particular factors
The model combines features that change in different ways as fibrosis develops: age and BMI reflect the metabolic background, diabetes is a powerful driver of NAFLD progression, and a rising AST/ALT ratio along with falling platelets and albumin are indirect signs of advanced liver damage.
Where it fits and other indices
NFS is about advanced fibrosis specifically in NAFLD. It complements other fibrosis scores: FIB-4 and FibroTest calculate fibrosis using different formulas, while LSS estimates tissue stiffness as a substitute for elastometry. It's convenient to compare the indices against each other, and the outcome is always interpreted by a physician.
Limitations and important caveats
- This is not a diagnosis. NFS estimates the probability of fibrosis, while it is confirmed by elastometry/elastography, ELF or biopsy.
- A score for NAFLD. It is validated specifically for fatty liver disease; interpret it cautiously if the damage has a different cause.
- It depends on data quality. Errors in height, weight, AST/ALT, platelets or albumin skew the result.
- The gray zone is a common outcome. It is not an error but a signal that additional methods are needed.
- It does not replace an examination. The result is interpreted by a physician, taking your history and comorbidities into account.
Frequently asked questions
Do I need to enter BMI manually?
No. Enter your height and weight — the calculator works out BMI itself (weight / height²) and plugs it into the formula.
What should I choose in the “Impaired glucose / diabetes” field?
“Yes” if you have been diagnosed with diabetes mellitus or impaired fasting glucose; otherwise “No.” This factor noticeably affects the result.
How does NFS differ from FIB-4?
Both scores assess fibrosis from lab tests, but using different formulas and sets of parameters. NFS uses BMI, albumin and diabetes and is tailored to NAFLD. It's useful to calculate them together.
Does a high NFS already mean cirrhosis?
No. A high result only raises the probability of advanced fibrosis (F3–F4) and requires confirmation by instrumental methods. The diagnosis is made by a physician.
What should I do with the result?
Show it to your physician along with your lab results. For a low result — monitoring and work on risk factors; for a gray or high one — elastometry/ELF and a follow-up plan.
