Clinical Overview
FIB-4 is a structured clinical decision-support tool. It is a low-cost first-line fibrosis risk estimate using routine laboratory data. It standardizes calculation and communication, but its output remains an estimate that must be interpreted with the complete history, examination, laboratory method, imaging, serial trend, and institutional protocol. Enter contemporaneous data and verify units before relying on the result.
The displayed category reflects cohorts and conventional thresholds rather than a diagnosis or mandatory treatment instruction. Document inputs with the result, reassess when the patient changes, and prioritize time-critical stabilization over score completion. Discordance between the calculated estimate and clinical concern should prompt review of measurements, assumptions, competing diagnoses, and specialist advice.
When to Use
- First-line fibrosis risk assessment in chronic liver disease
- MASLD/NAFLD and viral hepatitis pathways
Limitations & Safety
It is a triage test, not a fibrosis stage; cutoffs depend on disease, age, and pathway. Performance varies with population, prevalence, disease stage, treatment era, and local laboratory reference intervals. Avoid extrapolation to groups excluded from validation, and do not use a low score to dismiss concerning symptoms or a high score to prove a diagnosis.
Clinical decisions should incorporate contraindications, comorbidities, patient preferences, and current regional guidance. Pregnancy, childhood, older age, critical illness, altered physiology, and organ failure often require population-specific interpretation. Clinipocket stores no entered patient values; record clinically relevant results in the approved medical record.
- Less reliable under age 35 and requires age-adjusted interpretation over 65
- Acute hepatitis, alcohol flare, thrombocytopenia from another cause, or drugs can distort results
Formula / Scoring Criteria
FIB-4 = age (years) × AST (U/L) ÷ [platelets (10⁹/L) × √ALT (U/L)]
Interpretation
- <1.3 — Low: Lower probability of advanced fibrosis. Periodic reassessment according to risk.
- 1.3–2.67 — Indeterminate: Cannot classify reliably. Second-line elastography or validated biomarker.
- >2.67 — High: Higher probability of advanced fibrosis. Specialist fibrosis assessment.
Evidence & References
- Sterling RK, et al. Development of a simple noninvasive index to predict fibrosis.
- EASL clinical practice guidelines on non-invasive tests.
Clinical FAQs
Why is age important?
Age is in the numerator, so false-positive high results become more common in older adults.
Can it be used during acute hepatitis?
Avoid doing so because transient AST/ALT elevation can distort the estimate.
Does a low score exclude all fibrosis?
No. It lowers probability of advanced fibrosis within a validated pathway.