APRI Calculator
APRI (AST-to-Platelet Ratio Index) is one of the original biopsy-free screening scores for liver fibrosis — it needs just two numbers already on routine blood work: your AST and your platelet count. Like its younger sibling FIB-4, it was built to help decide who is unlikely to have significant fibrosis and who deserves a closer look.
From your liver or metabolic panel (sometimes labeled SGOT)
Printed next to the reference range on your report — commonly 35–40 U/L
From your CBC — same as K/µL on a US lab report
Enter your values above to see your results.
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How it works
The formula
APRI = (AST ÷ AST upper limit of normal) × 100 ÷ platelet count. AST and its ULN in U/L, platelets in 10⁹/L (the same number as K/µL on US reports). Example: AST 38, ULN 40, platelets 220 → (38 ÷ 40) × 100 ÷ 220 ≈ 0.43.
Why the ULN matters
APRI normalizes your AST against the upper limit of normal printed on your report, because labs use different reference ranges. Entering the wrong ULN shifts the score — check the number next to the AST reference range on your own report rather than assuming 40.
APRI vs FIB-4
Both are platelet-based fibrosis screening scores built from routine labs. FIB-4 adds age and ALT to the equation and has largely superseded APRI in NAFLD/MASLD pathways, while APRI remains widely used in viral hepatitis contexts and is simpler to compute. Searching for one usually means the other is relevant too — see our FIB-4 Calculator for the four-input version.
Evidence level & limitations
The 0.5 / 1.5 / 2.0 cutoffs come from hepatitis C validation cohorts (2003 onward) — extrapolation to NAFLD/MASLD and other liver conditions is weaker, and no cutoff is an official guideline grade for every population. Acute hepatitis flares, non-liver causes of low platelets, and lab-to-lab reference differences can all skew the inputs. APRI is a screening signal, not a diagnosis.
Frequently asked questions
How do I calculate my APRI score?
Divide your AST by its upper limit of normal (printed on your report), multiply by 100, then divide by your platelet count. Three numbers, one division each — the calculator above does it instantly and shows which band the result falls in.
What is a good APRI score?
Below 0.5 is the classic rule-out zone — in validation studies, scores there made significant fibrosis unlikely. Between 0.5 and 1.5 is indeterminate, and 1.5 or above is a higher-risk signal that warrants a medical workup (2.0 and above correlated with cirrhosis in the original HCV cohorts).
Where do I find the three values on my lab report?
AST is on a standard liver or metabolic panel (sometimes labeled SGOT), its upper limit of normal is printed next to it in the reference-range column, and platelets are on your CBC. All three are routine — any general blood draw in the past year likely includes them.
Is APRI or FIB-4 better?
They answer the same screening question with slightly different inputs. FIB-4 (which adds age and ALT) has become the more common choice in NAFLD/MASLD pathways, while APRI has a longer track record in viral hepatitis. If a clinician gave you one score, the other is usually computable from the same blood draw — our FIB-4 Calculator covers the four-input version.
Is a high APRI score the same as a cirrhosis diagnosis?
No. APRI is a screening score built to flag who might benefit from further evaluation — it does not diagnose cirrhosis or any other condition. A score of 2.0 or above is a reason to talk to a clinician promptly, not a conclusion.
My AST is normal — can APRI still be elevated?
Yes, because platelets are the denominator. A low platelet count — from any cause, not just liver-related — pushes APRI upward even with a completely normal AST. That's one reason an elevated score is a prompt for a workup rather than an answer.
Sources
- Wai CT et al. A simple noninvasive index can predict both significant fibrosis and cirrhosis in patients with chronic hepatitis C. Hepatology, 2003.
- Lin ZH et al. Performance of APRI and FIB-4 for assessing fibrosis in chronic hepatitis B and C — comparative validation cohorts.
- Chou R, Wasson N. Blood tests to diagnose fibrosis or cirrhosis in chronic liver disease — comparative accuracy review, Annals of Internal Medicine, 2013.
This calculator is for informational purposes only and is not medical advice, diagnosis, or treatment. Reference ranges are general population guidelines — always discuss your lab results with a qualified healthcare professional.