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FIB 4 Index Calculator

Work out fib 4 index instantly with clear inputs, formula shown and shareable results.

About FIB 4 Index Calculator

Combines age, transaminases and platelet count into the FIB-4 index, the first-line non-invasive test for advanced liver fibrosis.

Formula

FIB-4

FIB-4 = age x AST / (platelets x sqrt(ALT)); under 1.30 low risk, over 2.67 high risk

Worked example

With the default values below, FIB 4 Index Calculator returns FIB-4 index of 1.775. Change any input above and every figure here is recalculated in your browser.

Inputs used

Ageaccepts 18–100 years
55 years
ASTaccepts 5–500 U/L
45 U/L
ALTaccepts 5–500 U/L
60 U/L
Platelet countaccepts 10–600 x10^9/L
180 x10^9/L

Results

FIB-4 index
1.775
Risk band
Indeterminate — consider elastography or a second-line test
AST to ALT ratio
0.75

Step by step

  1. 1Values used
  2. 2FIB-4
  3. 3FIB-4 index= 1.775
  4. 4Risk band= Indeterminate — consider elastography or a second-line test
  5. 5AST to ALT ratio= 0.75

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.
  • This is an estimate for general information and not professional medical advice. See the full disclaimer for the limits that apply to this kind of calculator.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.

Frequently Asked Questions

Does the cut-off change with age?

Yes. A higher lower-cut-off of about 2.0 is recommended above age 65 to reduce false positives.

What follows an indeterminate result?

Transient elastography or an enhanced liver fibrosis blood panel is the usual second step.

Related Calculators

FIB 4 Index Calculator – Calculate FIB-4 index & Risk band