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APRI Liver Fibrosis Index Calculator — result sheet
Calculate the AST-to-platelet ratio index from AST, the laboratory’s AST upper limit of normal, and platelet count.
Inputs used
Results
Visual chart
Breakdown
Calculation steps
Returned data table
Formula and methodology
Formula: APRI = [(AST ÷ AST upper limit of normal) × 100] ÷ platelet count.
This calculator keeps the laboratory-specific AST upper limit visible rather than silently assuming one universal value. It returns the APRI arithmetic plus the AST-to-ULN multiple and percentage. It does not apply fibrosis cutoffs or make a liver-disease determination.
This result follows the calculator's declared inputs, precision, validation boundaries, and model limits.
Input contract
- AST activity — IU/L; minimum 0; maximum 100000
- AST upper limit of normal — IU/L; minimum 1.0E-6; maximum 100000
- Platelet count — 10⁹/L; minimum 1.0E-6; maximum 10000
Worked example
| Input | Value |
|---|---|
| AST activity | 82 |
| AST upper limit of normal | 40 |
| Platelet count | 90 |
AST/ULN is 2.05× and APRI is (2.05×100)÷90 = 2.2778.
Assumptions and limits
- AST and its upper limit use the same IU/L convention and laboratory method.
- Platelet count is entered in 10⁹/L, matching the published formula convention.
- The laboratory-specific upper limit of normal is positive and supplied by the user.
- The result is an index calculation, not a biopsy, imaging, or diagnosis.
- Population cutoffs, disease prevalence, age, sex, medications, and comorbidities are not inferred.
- Interpretation and follow-up require the patient’s clinician and the reporting laboratory.
Calculator note
Source and methodology
Use the official WorldCalculate methodology policy for the source, formula, precision, and boundary standards behind this calculator.
Planning estimate, not financial, medical, legal, or professional advice. © WorldCalculate — reuse with attribution. Built and curated by Hassan ALRowaie.
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