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FIB-4 Index for Liver Fibrosis

Estimates the degree of liver fibrosis in patients with chronic liver diseases, such as NAFLD and Hepatitis C.

The FIB-4 Index is a validated non-invasive test (NIT) used for the initial risk stratification of advanced liver fibrosis (F3-F4).

Medical Specialty:
hepatology

Patient Data

. Enter the value for Age in years.
. Enter the value for AST in U/L.
. Enter the value for Platelet Count in x10⁹/L.
. Enter the value for ALT in U/L.

Fill in all required fields to see the result

FOR PROFESSIONAL USE ONLY

This calculator is a support tool intended exclusively for health professionals. It does not replace clinical judgment. The final decision regarding diagnosis and treatment is the sole responsibility of the professional.

About this Calculator 💡

The FIB-4 Index is a validated non-invasive test (NIT) used for the initial risk stratification of advanced liver fibrosis (F3-F4). Its clinical interpretation and diagnostic accuracy depend strictly on the etiology and the patient's age:

• HCV & General Population: Validated cutoffs are < 1.45 (high NPV to exclude advanced fibrosis) and > 3.25 (high PPV for advanced fibrosis/cirrhosis).

• MASLD (formerly NAFLD): Employs stricter thresholds. A score < 1.30 excludes advanced fibrosis, while > 2.67 indicates a high probability.

• Age-Adjusted Cutoff (≥ 65 years): Because age is a continuous linear multiplier in the FIB-4 numerator, baseline specificity decreases in older adults. Per AGA/AASLD guidelines, the lower cutoff for MASLD patients aged 65 or older is adjusted to < 2.00 to mitigate false-positive referrals.

Scores falling within the indeterminate zone require sequential testing with second-line NITs (e.g., VCTE/FibroScan or ELF test) prior to considering liver biopsy.

Reference Values

  • •HCV: Low risk for advanced fibrosis (< 1.45)
  • •HCV: Indeterminate risk (1.45 - 3.25)
  • •HCV: High risk for advanced fibrosis (> 3.25)
  • •NAFLD/MASLD: Low risk for advanced fibrosis (< 1.30)
  • •NAFLD/MASLD: Low risk for advanced fibrosis (Age-adjusted < 2.00)
  • •NAFLD/MASLD: Indeterminate risk
  • •NAFLD/MASLD: High risk for advanced fibrosis (> 2.67)

Formula

Calculation Methodology (Age x AST) / (Platelets x √ALT)

Reference

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