APRI Liver Score Calculator
Estimate liver fibrosis from AST and platelet count.
Result
How it is calculated
The tool computes APRI = (AST ÷ AST upper limit of normal) × 100 ÷ platelets. AST is your result in U/L, the upper limit of normal is the reference limit printed by the same lab in the same units, and platelets are the count in 109/L (also written ×10³/µL). Dividing AST by its limit turns it into a multiple of normal, so labs with different limits can be compared. The score is shown to two decimals and read against fixed bands: below 0.5 means significant fibrosis is unlikely, 0.5 to 1.5 (both ends included) is indeterminate, and above 1.5 means significant fibrosis or cirrhosis is likely. AST and its limit must be above 0, and platelets must lie between 1 and 10,000, so a raw count such as 150,000 per µL is rejected and shows no result. It is a screening ratio, not a diagnosis.
Worked example
A lab reports AST 60 U/L with an upper limit of normal of 40 U/L, and platelets 150 (109/L). AST is 60 ÷ 40 = 1.5 times the limit. Multiply by 100 to get 150, then divide by the platelets: 150 ÷ 150 = 1.00. This sits between 0.5 and 1.5, so the tool labels it Indeterminate. With the same AST and platelets of 250 the score would be 0.60, still indeterminate; with platelets of 90 and AST 120 it would be 3.33, in the likely-fibrosis band.
Common mistakes
- Using an AST upper limit from another lab. The ratio depends on the reference limit of the lab that ran the test, which differs between labs, so use the one printed on your report.
- Entering platelets as the raw count, such as 150,000 per µL. The field is in 109/L, so type 150. Values above 10,000 give no result, but a count mistakenly typed as 1500 would still calculate and understate the score.
- Entering AST as a ratio already divided by its limit. The tool divides by the limit itself, so enter the absolute AST value in U/L.
- Reading an indeterminate score as normal or as disease. The middle band 0.5 to 1.5 means more testing is needed, not a result either way.
- Using a result taken during an acute flare, when AST is temporarily high, and treating the score as a long-term measure.
About this calculator
The AST-to-Platelet Ratio Index (APRI) is a non-invasive liver fibrosis screening score calculated from two numbers routinely available on a standard blood panel — AST (aspartate aminotransferase) expressed as a multiple of the upper limit of normal, divided by platelet count (in 10⁹/L), then multiplied by 100. It works on the principle that liver damage raises AST while advancing fibrosis and portal hypertension progressively lower platelet counts, so a rising ratio tracks with worsening liver disease.
Hepatologists and primary care clinicians use APRI most often in chronic hepatitis B and C patients as a first-pass alternative to liver biopsy or elastography, particularly in settings where those tools aren't readily available — a low score helps rule out significant fibrosis, while a high score flags patients who need further workup such as imaging or biopsy. It's a screening aid, not a diagnostic replacement, so results are interpreted alongside other clinical findings.
This calculator takes your AST value, the lab's upper limit of normal for AST, and your platelet count, and returns your APRI score along with which fibrosis-risk range it falls into.
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