Calculate the APRI score for non-invasive liver fibrosis assessment. Also compares FIB-4 and AST:ALT ratio for broader liver-fibrosis review.
The APRI Score Calculator computes the AST to Platelet Ratio Index for non-invasive review of liver fibrosis risk. It also calculates FIB-4 and the AST:ALT ratio so the result can be reviewed as part of a broader liver-fibrosis worksheet rather than as a single isolated score.
APRI was developed by Wai et al. in 2003 as a simple, widely accessible fibrosis marker, especially in chronic hepatitis C. Because it uses only AST and platelet count, it remains useful in settings where elastography or biopsy are not immediately available.
This page is best read as a fibrosis triage tool. Low and high scores are often the most informative, while indeterminate scores usually need elastography, specialist follow-up, or other confirmatory assessment before advanced fibrosis is ruled in or ruled out.
APRI uses routine lab values that are available almost everywhere, making it a practical first-pass fibrosis screen. Showing APRI alongside FIB-4 helps frame whether the result looks reassuring, indeterminate, or concerning enough to justify more definitive follow-up such as elastography.
APRI = ((AST / AST Upper Limit of Normal) / Platelet Count (×10⁹/L)) × 100 FIB-4 = (Age × AST) / (Platelet Count × √ALT) De Ritis Ratio = AST / ALT APRI Cutoffs: <0.5 = no significant fibrosis, 0.5-1.5 = indeterminate, ≥1.5 = significant fibrosis/cirrhosis, ≥2.0 = cirrhosis FIB-4 Cutoffs: <1.45 = low risk, 1.45-3.25 = indeterminate, >3.25 = advanced fibrosis
Result: APRI = 1.08 (Indeterminate), FIB-4 = 1.52 (Indeterminate), De Ritis = 1.44
With AST 65 U/L (1.625× ULN) and platelets 150, APRI is 1.08, falling in the indeterminate range. FIB-4 of 1.52 also falls in the indeterminate zone. Both scores suggest further workup (FibroScan or biopsy) is needed.
The World Health Organization's 2015 guidelines for chronic hepatitis B and C recommend APRI as the preferred non-invasive test in resource-limited settings where FibroScan is not available. An APRI >2.0 is recommended as the cutoff for cirrhosis, and APRI <0.5 for ruling out significant fibrosis, with intermediate values requiring further assessment when possible.
FIB-4 was developed from the HALT-C trial and incorporates age, AST, ALT, and platelet count. It has been validated in multiple liver disease etiologies and generally outperforms APRI, particularly for distinguishing advanced fibrosis (F3-F4). The combination of APRI and FIB-4 results in better classification than either alone.
In modern hepatology, non-invasive fibrosis assessment is mainly used to decide who can be reassured, who should get elastography or specialist review, and who may already be in a high-risk fibrosis range. The page should be read as a triage aid rather than a stand-alone fibrosis diagnosis.
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This page calculates APRI as "((AST / AST upper limit of normal) / platelet count) × 100", then shows the result alongside FIB-4 and the AST:ALT ratio so the liver-fibrosis screen can be reviewed as a bundle rather than as a single score. The score bands are presented as non-invasive triage ranges that help separate low, indeterminate, and higher-risk fibrosis patterns.
The result is intended for fibrosis risk stratification rather than for definitive fibrosis staging. APRI performs best at the low and high ends, while indeterminate values usually need elastography, specialist review, or other follow-up before advanced fibrosis is confirmed or excluded.
For cirrhosis (F4), APRI has an AUROC of 0.77 using a cutoff of 2.0 (sensitivity 48%, specificity 94%). For significant fibrosis (F2-F4), AUROC is 0.76 using a cutoff of 0.5. It performs best at the extremes (ruling in or ruling out) with an indeterminate zone in between.
Use both together. FIB-4 generally has better discrimination (AUROC 0.85), especially in patients over 35. APRI has the advantage of requiring only 2 values. If both agree, confidence is higher; if they disagree, further testing is warranted.
APRI performs less well in MASLD/NAFLD compared to viral hepatitis. For MASLD, the NFS (NAFLD Fibrosis Score) or FIB-4 are preferred non-invasive tests. FibroScan is the best non-invasive option.
Thrombocytopenia (<150 ×10⁹/L) in liver disease often reflects portal hypertension or hypersplenism, both indicators of advanced fibrosis or cirrhosis. This is why platelets are central to the APRI formula.
Use your specific laboratory's upper limit of normal, as it varies by assay and lab (typically 35-40 U/L). Using an incorrect ULN will systematically shift your APRI score.
For chronic liver disease under treatment, recheck every 6-12 months. Sustained improvement (especially with HCV cure or HBV suppression) may indicate fibrosis regression.