NAFLD Fibrosis Score Calculator
NAFLD Fibrosis Score Calculator
Estimate advanced fibrosis in fatty liver disease from age, BMI, glycaemic status, AST/ALT ratio, platelets and albumin.
NAFLD Fibrosis Score
6 inputs → scoreAge 55, BMI 32, diabetes present, AST 48, ALT 40, platelets 190, albumin 3.8 g/dL
Formula
- age
- years
- BMI
- kg/m²
- IFG/diabetes
- 1 if present, 0 if absent
- AST/ALT
- ratio of the two in U/L
- platelets
- ×10⁹/L
- albumin
- g/dL — divide g/L by 10
Worked example
Age 55, BMI 32, diabetes present, AST 48, ALT 40, platelets 190, albumin 3.8 g/dL
AST/ALT = 48 ÷ 40 = 1.20
−1.675 + (0.037×55) + (0.094×32) + 1.13 + (0.99×1.20) − (0.013×190) − (0.66×3.8)
= −1.675 + 2.035 + 3.008 + 1.130 + 1.188 − 2.470 − 2.508 = 0.708
Above 0.675 → advanced fibrosis likely
Thresholds
| Score | Interpretation | Predictive value |
|---|---|---|
| < −1.455 | Advanced fibrosis unlikely | NPV ≈ 93% |
| −1.455 to 0.675 | Indeterminate | — |
| > 0.675 | Advanced fibrosis likely | PPV ≈ 90% |
Using the score in a fatty liver pathway
The NAFLD fibrosis score was derived specifically in biopsied fatty liver disease, and unlike the more general indices it includes BMI and glycaemic status — the two metabolic drivers that determine who progresses. That makes it better calibrated than APRI in this population, though FIB-4 is simpler and performs comparably.
It is used the same way as FIB-4: as a rule-out test at the front of a pathway. A score below −1.455 makes advanced fibrosis unlikely enough to keep a patient in primary care, which is what a condition affecting a quarter of the adult population requires. A score above 0.675 warrants referral.
Two limitations matter in practice. About a third of patients land in the indeterminate band and need a second test regardless, so many pathways now run FIB-4 first and reserve elastography for the indeterminate and high groups. And like FIB-4, the score drifts upward with age because age is a positive term, so it over-calls fibrosis in older patients — the same caution that produced the age-adjusted FIB-4 threshold applies here, without an agreed correction.
Frequently asked questions
What albumin units does the NAFLD fibrosis score use?
g/dL. If your laboratory reports g/L, divide by 10 — an albumin of 38 g/L is 3.8 g/dL. Using g/L directly produces a wildly wrong score.
What counts as impaired fasting glucose for this score?
A fasting glucose of 100 mg/dL (5.6 mmol/L) or above, or an established diagnosis of diabetes. Either scores 1.
How does it compare with FIB-4?
Similar accuracy in fatty liver disease. FIB-4 needs fewer inputs and no BMI, so most pathways use it first; the NAFLD fibrosis score adds metabolic variables and is a reasonable second opinion.
What do I do with an indeterminate result?
Proceed to a second non-invasive test — transient elastography or an ELF blood test — rather than to biopsy. Around a third of patients score in this band.
Related calculators
References
- Angulo P et al. The NAFLD fibrosis score: a noninvasive system that identifies liver fibrosis in patients with NAFLD. Hepatology. 2007;45(4):846–54.
- EASL-EASD-EASO Clinical Practice Guidelines on the management of MASLD.