APRI Calculator — AST-to-Platelet Ratio Index
The APRI (AST-to-Platelet Ratio Index) is a validated non-invasive blood test score used to estimate the likelihood of significant liver fibrosis or cirrhosis — most widely studied in chronic hepatitis C. Enter your AST, its lab upper limit of normal, and your platelet count.
U/L
U/L
10⁹/L
Indeterminate — further evaluation recommended
- 1
AST / ULN ratio
55 ÷ 40 = 1,375 - 2
Divide by platelet count
1,375 ÷ 120 = 0,011458 - 3
APRI score (× 100)
0,011458 × 100 = 1,146Multiply by 100 to express the ratio as a per-100-unit index.
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APRI = (AST ÷ AST_ULN) ÷ Platelet_count × 100. An APRI below 0.5 suggests low fibrosis risk; above 1.5 suggests significant fibrosis; above 2.0 may indicate cirrhosis. Results must be interpreted by a physician alongside clinical findings.
Formel
How this is calculated
The APRI score was introduced by Wai et al. (2003) as a simple, laboratory-based alternative to liver biopsy for staging fibrosis in chronic hepatitis C. It exploits two independent signals of liver disease: AST (aspartate aminotransferase), which rises as hepatocytes are damaged, and the platelet count, which falls as portal hypertension develops in advancing fibrosis and spleen enlargement traps platelets. Dividing the normalised AST ratio by platelet count (in units of 10⁹/L) and multiplying by 100 yields a unitless score.
Published cut-offs (for chronic hepatitis C) are: APRI < 0.5 rules out significant fibrosis (≥F2) with a negative predictive value of roughly 85–95%; APRI > 1.5 rules in significant fibrosis with a positive predictive value of roughly 75–88%; the range 0.5–1.5 is indeterminate and typically warrants fibroscan, FIB-4, or biopsy. A score above 2.0 is associated with cirrhosis (F4) in many cohorts. The WHO recommends APRI as a first-line fibrosis screening tool where fibroscan is unavailable.
Limitations: APRI was validated primarily in hepatitis C; its accuracy is lower in hepatitis B, NAFLD, and other aetiologies. AST can be elevated by non-hepatic causes (cardiac, muscular, haemolysis), artificially inflating the score. The ULN value differs between laboratories and between male and female reference ranges (approximately 40 U/L for males, 31 U/L for females in many guidelines) — always use the ULN from your own laboratory report. This calculator is a screening aid and does not replace clinical evaluation.
Ofte stillede spørgsmål
An APRI above 1.5 is associated with a high probability of significant fibrosis (METAVIR stage ≥F2) in hepatitis C populations. APRI below 0.5 has a high negative predictive value for significant fibrosis. Scores between 0.5 and 1.5 are indeterminate.
Always use the upper limit of normal printed on your specific laboratory report. A common adult reference is 40 U/L for males and 31 U/L for females, but this varies between laboratories and analysers. Using the wrong ULN will give an inaccurate APRI score.
Both APRI and FIB-4 are validated non-invasive fibrosis scores. FIB-4 (which adds age and ALT) tends to have slightly better diagnostic accuracy in hepatitis B and NAFLD. APRI requires only AST and platelets, making it simpler. Many guidelines recommend using both together.
Også kendt som
TG we-Calculate Editorial Team. (2026). APRI Calculator — AST-to-Platelet Ratio Index [Online calculator]. TG we-Calculate. https://we-calculate.com/da/calculator/apri-calculator
TG we-Calculate Editorial Team. "APRI Calculator — AST-to-Platelet Ratio Index." TG we-Calculate. 2026. https://we-calculate.com/da/calculator/apri-calculator.
TG we-Calculate Editorial Team, "APRI Calculator — AST-to-Platelet Ratio Index," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/da/calculator/apri-calculator
@misc{wecalculate_apri_calculator, title = {APRI Calculator — AST-to-Platelet Ratio Index}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/da/calculator/apri-calculator}}, year = {2026}, note = {TG we-Calculate} }
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