Maddrey Discriminant Function Calculator
Calculate the Maddrey Discriminant Function (MDF) for alcoholic-hepatitis severity context and compare it with related liver-severity markers such as MELD.
FIB-4 Index Calculator — Hepatic Fibrosis
Calculate the FIB-4 index for liver fibrosis risk screening using age, AST, ALT, and platelets, with age-adjusted cutoffs and APRI comparison.
⚠️ Medical Disclaimer: FIB-4 is a screening tool for advanced fibrosis. It does not diagnose cirrhosis and cannot replace liver biopsy or elastography in all cases. Always interpret in clinical context.
Presets:
years
U/L
U/L
×10⁹/L
Planning notes, formulas, and examples
About the FIB-4 Index Calculator — Hepatic Fibrosis
The FIB-4 Index Calculator estimates liver-fibrosis risk using four routine laboratory values: age, AST, ALT, and platelet count. Originally developed by Sterling et al. (2006) for HIV-HCV coinfection, FIB-4 has since been validated across a wide range of chronic liver diseases including MASLD, hepatitis B, hepatitis C, and alcohol-related liver disease.
FIB-4 is widely used as a first-line non-invasive fibrosis screen because its strongest feature is a high negative predictive value: a clearly low score helps rule out advanced fibrosis in many outpatient settings. Scores in the indeterminate or high-risk range are usually treated as a reason for elastography or specialist review rather than as a definitive fibrosis diagnosis.
This page applies age-adjusted cutoffs used in contemporary screening pathways and also computes APRI for comparison. The output is meant to help triage next steps, not to replace elastography, biopsy, or full hepatology evaluation.
When This Page Helps
FIB-4 turns routine labs into a practical first-line fibrosis screen. Its main value is ruling out advanced fibrosis when the score is low and helping decide who needs elastography or hepatology review when the score is not clearly low.
How to Use the Inputs
- Enter patient age in years.
- Enter AST (SGOT) level in U/L (international units per liter).
- Enter ALT (SGPT) level in U/L.
- Enter platelet count in ×10⁹/L (thousands per microliter).
- Select the liver disease etiology for context-appropriate interpretation.
- Review FIB-4 score, fibrosis risk category, and recommended next steps.
Formula used
FIB-4 = (Age [years] × AST [U/L]) / (Platelet count [×10⁹/L] × √ALT [U/L])
Standard cutoffs (age 35–65):
• <1.30 = Low risk of advanced fibrosis (F3–F4)
• 1.30–2.67 = Indeterminate
• >2.67 = High risk of advanced fibrosis
Age-adjusted (age <35): <0.70 low risk
Age-adjusted (age ≥65): <2.00 low risk
APRI = (AST / Upper Limit Normal) / Platelets × 100Example Calculation
Result: FIB-4 = 2.91 — High risk of advanced fibrosis.
FIB-4 = (55 × 55) / (150 × √48) = 3025 / (150 × 6.93) = 3025 / 1039.5 = 2.91. This is above the 2.67 high-risk cutoff, so the score falls in a range associated with advanced fibrosis risk. The next step is usually confirmation with elastography or specialist review rather than relying on the score alone.
Tips & Best Practices
- FIB-4's greatest strength is its negative predictive value (90–95%) — a low score reliably rules OUT advanced fibrosis.
- Age-adjusted cutoffs are important: standard cutoffs overestimate fibrosis risk in elderly patients and may underestimate it in young patients.
- Platelets decrease with portal hypertension (splenic sequestration), which is why thrombocytopenia helps identify advanced liver disease.
- AST/ALT ratio >1 suggests advanced fibrosis or cirrhosis in most liver diseases (except Wilson disease where this ratio is unreliable).
- Recheck FIB-4 after treating the underlying cause (e.g., after virologic cure in HCV or after weight loss in NAFLD) — fibrosis can regress with treatment.
- Acute hepatitis episodes (viral flares, DILI) will transiently elevate AST/ALT and give falsely high FIB-4 scores — wait for resolution before calculating.
FIB-4 in Clinical Practice
Contemporary liver-disease pathways commonly use FIB-4 as an initial non-invasive screen. The general workflow is: calculate FIB-4 from routine labs, reassure and recheck later if it is clearly low, move to elastography if it is indeterminate, and treat high scores as a reason for further staging rather than as proof of cirrhosis.
Monitoring Fibrosis Over Time
FIB-4 can also be followed over time after treatment of the underlying liver disease, but the score should be interpreted cautiously because changes in transaminases, platelet count, and age all affect the number. It is better for broad risk stratification than for measuring short-term histologic change.
Limitations to Remember
FIB-4 should not be treated as a universal fibrosis diagnosis. Acute hepatitis, pregnancy, age extremes, isolated thrombocytopenia, and non-hepatic AST elevation can all distort the score. Like APRI, it works best as a triage tool that helps decide when more definitive staging is needed.
Sources & Methodology
Last updated:
Methodology
This page calculates FIB-4 as "(age × AST) / (platelet count × √ALT)", then applies age-adjusted low- and high-risk thresholds so the result can be read the way current fibrosis-screening pathways use it. It also shows APRI for comparison, but the main purpose of the page is to separate low-risk results from the indeterminate and higher-risk ranges that usually trigger further staging.
The result is intended as a non-invasive fibrosis triage score, not as a stand-alone diagnosis of cirrhosis or advanced fibrosis. Acute hepatitis, pregnancy, non-hepatic AST elevation, age extremes, and isolated thrombocytopenia can all distort the score, so elastography or specialist evaluation is still needed when the result is not clearly low-risk.
Sources
- Development of a simple noninvasive index to predict significant fibrosis in patients with HIV/HCV coinfection (Hepatology) — Original FIB-4 publication by Sterling et al.
- AASLD Practice Guidance on the clinical assessment and management of nonalcoholic fatty liver disease (Hepatology) — Guideline context for first-line fibrosis screening and age-adjusted FIB-4 use.
Frequently Asked Questions
FIB-4 is a composite score that estimates the likelihood of advanced liver fibrosis (METAVIR F3–F4). It combines four variables that individually reflect liver injury and portal hypertension: age (fibrosis accumulates over time), AST (marker of hepatocyte damage), ALT (hepatocyte damage — the AST/ALT ratio increases with fibrosis), and platelet count (decreases with portal hypertension and decreased thrombopoietin production). FIB-4 does not directly measure fibrosis — it statistically estimates the probability based on surrogate markers.
For patients with low FIB-4 (<1.30): recheck every 1–2 years if the underlying liver disease persists (e.g., ongoing NAFLD, untreated hepatitis B). For the indeterminate zone: recheck after any intervention (weight loss, viral treatment, alcohol cessation) to see if the score improves below the low-risk cutoff. FIB-4 should not be recalculated during acute events (viral hepatitis flares, DILI) as transient transaminase elevations will give falsely elevated scores.
FIB-4 is a blood-test-based calculation (no equipment needed, available anywhere, free). FibroScan (transient elastography) is an ultrasound-based device that directly measures liver stiffness in kilopascals (kPa). FibroScan is more accurate but requires specialized equipment, trained operators, and costs more. A common clinical pathway is: FIB-4 first (screening) → FibroScan for patients in the indeterminate zone (confirmation). This sequential approach reduces unnecessary FibroScan referrals by ~50%.
Yes — FIB-4 has been extensively validated in NAFLD/MASLD populations and is recommended as the first-line screening test by AASLD, EASL, and ACG guidelines. In NAFLD, FIB-4 <1.30 has a NPV of ~90% for excluding advanced fibrosis. The main limitation is the large indeterminate zone (~30–40% of NAFLD patients fall between 1.30–2.67), which is why the sequential approach with FibroScan or ELF test is recommended. The NAFLD Fibrosis Score (NFS) is an alternative that incorporates BMI, diabetes status, and albumin.
No — FIB-4 was designed and validated specifically for detecting advanced fibrosis (F3–F4). It has poor sensitivity and specificity for distinguishing F0-F1 from F2. This is a known limitation of all non-invasive fibrosis tests (including elastography to some degree). For early fibrosis detection, liver biopsy remains the gold standard. However, from a clinical management perspective, the most important distinction is between F0-F2 (favorable prognosis) and F3-F4 (significantly increased morbidity/mortality), which FIB-4 addresses well.
Age is a component of the FIB-4 formula (numerator), so older patients inherently get higher scores regardless of fibrosis status. Using the standard <1.30 cutoff in patients ≥65 leads to excessive false positives (~50–60% of elderly patients without fibrosis score >1.30). AASLD guidance discusses a <2.0 low-risk cutoff for age ≥65. Conversely, young patients (<35) may have falsely reassuring low FIB-4 values; a lower cutoff of 0.70 improves sensitivity in this age group.
More in this topic
Fractional Excretion of Sodium (FENa) Calculator
Calculate FENa to differentiate prerenal from intrinsic renal AKI. Includes FENa formula, AKI diagnostic indices comparison, and clinical interpretation with diuretic use guidance.
Glomerular Filtration Rate (GFR) Calculator
Estimate kidney filtration with CKD-EPI, MDRD, Cockcroft-Gault, and cystatin C equations. Includes CKD stage context, albuminuria, and equation comparison for medication review or referral discussions.