NAFLD Fibrosis Score

Background

The NAFLD fibrosis score (NFS) estimates the likelihood of advanced (F3–F4) liver fibrosis in non-alcoholic fatty liver disease using six routinely available variables: age, body-mass index, the presence of impaired fasting glucose or diabetes, the AST/ALT ratio, platelet count and albumin. These are combined in a weighted regression equation to produce a single value. It was developed to help identify, without biopsy, which patients with fatty liver are likely to have advanced fibrosis and therefore need specialist assessment. It is one of the most widely used non-invasive fibrosis scores in this population.

Interpreting the result

The score is read against two cut-offs: a value below −1.455 indicates F0–F2, making advanced fibrosis unlikely; a value above 0.675 indicates F3–F4, making advanced fibrosis likely; and values between the two are indeterminate. The two-threshold design deliberately creates a low-risk and a high-risk zone with high predictive value, at the cost of a sizeable indeterminate middle group. Patients in the high-risk band warrant specialist referral and further fibrosis testing, while those in the indeterminate zone typically need additional assessment such as elastography or FIB-4.

Worked example

A 60-year-old with diabetes, a BMI of 32, AST 50 U/L, ALT 40 U/L, platelets 140 ×10⁹/L and albumin of 3.8 g/dL has a NAFLD fibrosis score above 0.675, placing them in the F3–F4 band where advanced fibrosis is likely and specialist assessment is warranted.

Pearls / pitfalls

• Enter albumin in g/dL (divide a g/L value by 10) to match the equation.
• The indeterminate zone is large, so a substantial proportion of patients need a second test such as elastography or FIB-4 rather than a definitive answer from the NFS alone.
• Its accuracy can fall at the extremes of age and in patients with diabetes, where thresholds may need cautious interpretation.
• It is specific to non-alcoholic fatty liver disease and should not be applied to other chronic liver diseases.

Evidence & validation

Derived and validated by Angulo and colleagues across NAFLD cohorts, the NFS is endorsed in fatty liver disease guidance (for example from EASL and NICE) as a first-line non-invasive tool to stratify the risk of advanced fibrosis and target further testing.

Frequently asked questions

References

1. Angulo P, Hui JM, Marchesini G, et al. The NAFLD fibrosis score: a noninvasive system that identifies liver fibrosis in patients with NAFLD. Hepatology. 2007;45(4):846–854.
2. European Association for the Study of the Liver (EASL). Clinical Practice Guidelines on non-invasive tests for evaluation of liver disease severity and prognosis. J Hepatol. 2021.

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