SAFE score
SAFE (Steatosis-Associated Fibrosis Estimator) is a scoring system that sorts people with NAFLD by the risk of significant liver fibrosis (F2 and above) and long-term outcomes. It is calculated from age, BMI, diabetes and routine blood tests — and assigns the result to low, intermediate or high risk.
What SAFE is and why it matters
SAFE (Steatosis-Associated Fibrosis Estimator) is a scoring system that classifies patients with NAFLD by the risk of significant liver fibrosis (F2 and above on METAVIR) and by long-term outcomes. It needs no equipment — only your age, height and weight (for BMI), information about diabetes and routine blood tests.
Non-alcoholic (metabolic dysfunction–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. It is the fibrosis stage that largely determines the prognosis.
What's needed for the calculation
SAFE is calculated from seven factors — two about you and five from lab tests:
- Age, years. It enters the calculation directly.
- BMI. The calculator computes it from your height and weight (values above 40 are capped).
- Diabetes. A binary yes/no factor — a significant marker of NAFLD progression.
- AST and ALT, U/L. Liver enzymes; they reflect damage to liver cells.
- Globulins, g/L. The calculator works them out as the difference: total protein − albumin.
- Platelets, ×10⁹/L. As fibrosis progresses their number usually falls.
How to prepare properly
Height and weight
Accuracy depends on measurement technique. Measure height without shoes; weigh yourself under consistent conditions — ideally in the morning, on an empty stomach and on the same scale.
Blood tests
Total protein, albumin, AST and ALT are part of a blood chemistry panel; platelets come from a complete (clinical) blood count (×10⁹/L). You don't need to test globulins separately — the calculator derives them as “total protein minus albumin.”
SAFE Calculator
Enter your age, height, weight, information about diabetes and lab tests — the calculator will compute BMI and globulins, calculate the SAFE score and determine the risk zone. The calculation runs on the server.
Zones (Sripongpun, 2023): < 0 — low risk · 0–99 — intermediate · ≥ 100 — high risk.
How to read the result
SAFE has two threshold points that split the result into three risk zones for significant fibrosis (F2+):
| SAFE | Risk |
|---|---|
| < 0 | Low risk |
| 0 – 99 | Intermediate risk |
| ≥ 100 | High risk |
Significant fibrosis is unlikely. Monitoring and work on NAFLD risk factors.
No definite conclusion is possible — further testing is needed (elastography/ELF).
A high likelihood of significant fibrosis; confirmation and a management plan are essential.
Why these particular factors
SAFE 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, the enzymes AST and ALT reflect liver damage, and a rise in globulins and a fall in platelets are indirect signs of advanced disease.
Its place in the section and other indices
SAFE is especially good at ruling out low risk in NAFLD and, according to its authors, outperforms FIB-4 and NFS at this task. It pairs well with other scores: FIB-4 and NFS assess the fibrosis stage, LSS — tissue stiffness, FNI — active fibrotic NASH. The conclusion is always interpreted by a physician.
Limitations and important caveats
- It is not a diagnosis. SAFE estimates the risk of significant fibrosis; it is confirmed by elastography, ELF or biopsy.
- A NAFLD score. It was developed for fatty liver disease; if the liver injury has a different cause, interpret it with caution.
- It depends on data quality. Errors in height, weight, protein, albumin, enzymes or platelets shift the result.
- The intermediate 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 test globulins separately?
No. Enter total protein and albumin — the calculator works out globulins as the difference between them.
How does SAFE differ from FIB-4 and NFS?
All three assess fibrosis in NAFLD, but with different formulas. SAFE is especially strong at reliably ruling out low risk and, according to its authors, outperforms FIB-4 and NFS at separating F0–F1 from ≥F2.
What does “high risk” mean?
An increased likelihood of significant fibrosis (F2+). It is not a diagnosis but a reason to have elastography and see a physician.
What should I do with the result?
Show it to your physician along with your test results. For low risk — monitoring and work on risk factors; for intermediate or high — elastography/ELF and a work-up plan.
