FIB-4

FIB-4

Principle

Use age at testing and results from the same laboratory assessment.

Scope

Adult · MASLD context · not for acute illness

Interpretation limits

MASLD: metabolic dysfunction-associated steatotic liver disease. The category depends on age and the unrounded value. Under EASL 2024, the lower threshold changes after age 65; the ADA 2026 convention from age 65 is not applied here. Elastography may complement assessment according to context. The score alone does not establish a diagnosis. Advanced fibrosis may be present despite a low result. This pathway does not cover acute illness, established cirrhosis, viral hepatitis or alcohol-related liver disease. Persistently abnormal transaminases require independent assessment.

Formula and logic

FIB-4 = [age (years) × AST (U/L)] / [platelets (10⁹/L) × √ALT (U/L)]

Inputs and original units

Platelets · G/L

Strictly positive value; check the unit on the laboratory report.

Interpretation

Below age 18

Outside the paediatric scope.

Ages 18–34

Limited interpretation below age 35. This result cannot rule out advanced fibrosis.

Ages 35–65 inclusive

Low: S < 1.30; intermediate: 1.30 ≤ S ≤ 2.67; high: S > 2.67.

Over age 65

Low: S < 2.00; intermediate: 2.00 ≤ S ≤ 2.67; high: S > 2.67.

Definition version : 1.0.0

Sources

• EASL–EASD–EASO — Clinical Practice Guidelines on the management of metabolic dysfunction-associated steatotic liver disease (MASLD)

  2024 · MASLD pathway, figure 2: lower threshold adapted above age 65; upper boundary included in the intermediate range.

• AASLD — Practice Guidance on the clinical assessment and management of nonalcoholic fatty liver disease

  2023 · Exclusion of acute illness, limited accuracy below age 35, additional assessment according to context.

• Sterling et al. — Development of a simple noninvasive index to predict significant fibrosis in patients with HIV/HCV coinfection

  2006 · Origin of the formula; historical HIV/HCV thresholds are not applied in this MASLD pathway.