Calculate the APRI score for non-invasive liver fibrosis assessment. Also computes FIB-4 index and De Ritis ratio with fibrosis staging and treatment guidance.
The APRI Score Calculator computes the AST to Platelet Ratio Index for non-invasive assessment of liver fibrosis and cirrhosis. It simultaneously calculates the FIB-4 index and AST:ALT (De Ritis) ratio, providing a comprehensive non-invasive fibrosis evaluation panel from standard laboratory values.
The APRI was developed by Wai et al. in 2003 as a simple, widely accessible marker for liver fibrosis, primarily validated in chronic hepatitis C. It uses only two laboratory values — AST and platelet count — making it ideal for resource-limited settings. The World Health Organization recommends APRI (along with FIB-4) as the preferred non-invasive test for assessing liver fibrosis in settings where FibroScan or liver biopsy are unavailable.
This calculator provides both APRI and FIB-4 scores, as using them together improves diagnostic accuracy. It includes the De Ritis ratio (AST:ALT), which adds additional clinical context regarding liver disease etiology. Results are mapped to METAVIR fibrosis stages (F0-F4) with clear action recommendations, performance data by liver disease etiology, and comparison against other fibrosis assessment methods.
The APRI requires only two standard lab values, making it the most accessible fibrosis screening tool worldwide. Calculating it alongside FIB-4 provides a comprehensive non-invasive fibrosis assessment that can guide referral decisions and reduce unnecessary liver biopsies. Keep these notes focused on your operational context. Tie the context to the calculator’s intended domain. Use this clarification to avoid ambiguous interpretation.
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 drives treatment priorities. Patients with significant fibrosis (F2+) are prioritized for antiviral therapy. Those with cirrhosis (F4) require HCC surveillance every 6 months and variceal screening. The shift from biopsy-based to biomarker-based assessment has substantially increased the number of patients who can be appropriately staged and treated.
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.