AST To Platelet Ratio Index (APRI) Calculator

Helps with cirrhosis diagnosis based on the platelet count and AST level.

In the text below the tool there is more information about the APRI score and about the original study.

The AST to platelet ratio index is a non invasive method that can offer information about risk of hepatic fibrosis and cirrhosis, based on platelet count and aspartate aminotransferase level.

APRI = AST (IU/L) / AST upper normal limit (IU/L) /Platelet count (109/L) x 100

This index is aimed at becoming the surrogate marker of liver fibrosis in hepatitis C virus patients and avoid unnecessary liver biopsy in low risk cases:

■ APRI values below 0.5 rule out significant fibrosis;

■ APRI values between 0.5 and 0.7 indicate some kind of liver damage;

■ APRI values above 1 were found to indicate cirrhosis (sensitivity 76%).

AST Level
Upper limit of Normal AST (IU/L)
Platelet Count (109/L)
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Steps on how to print your input & results:

1. Fill in the calculator/tool with your values and/or your answer choices and press Calculate.

2. Then you can click on the Print button to open a PDF in a separate window with the inputs and results. You can further save the PDF or print it.

Please note that once you have closed the PDF you need to click on the Calculate button before you try opening it again, otherwise the input and/or results may not appear in the pdf.


Variables and formula

The APRI uses the following patient parameters:

■ AST (aspartate aminotransferase), measured in IU/L;

■ The upper AST limit, set default at 40 IU/L but customizable;

■ Platelet count measured in 109 cells per L.

The formula used to calculate the index is:

APRI = AST (IU/L) / AST upper normal limit (IU/L) /Platelet count (109/L) x 100

The use of the index can reduce unnecessary liver biopsy investigations in patients who are deemed to carry a low risk of liver fibrosis.

The APRI was also found to be useful in the diagnosis of non-alcoholic fatty liver disease (NAFLD), as the index increase with the degree of fibrosis.


APRI interpretation

The aspartate aminotransferase to platelet ratio index suggests the level of hepatic fibrosis and possible liver disease:

APRI Fibrosis degree
<0.5 Ruled out
0.5 – 0.7 Associated with some kind of liver damage
0.7 - 1 Significant fibrosis
>1 Associated with cirrhosis

The 0.7 threshold was found to be 77% sensitive & 72% specific whilst the 1.0 threshold was found to be 61% sensitive & 64% specific for severe fibrosis and 76% sensitive & 72% specific for cirrhosis.


About the study

In 2011, Lin et al. constructed the aspartate aminotransferase-to-platelet ratio index (APRI) which meant hepatic fibrosis could be detected via a non-invasive method.

The study analysed previous research on hepatitis C virus (HCV) monoinfected and HCV / human immunodeficiency virus (HIV) coinfected patients.

The APRI accuracy for the diagnosis of significant fibrosis, severe fibrosis, and cirrhosis was analysed via:

■ Areas under summary receiver operating characteristic curves (AUROC);

■ Sensitivity;

■ Specificity;

■ Positive predictive value (PPV);

■ Negative predictive value (NPV).

It was found that APRI can identify hepatitis C-related fibrosis with a moderate degree of accuracy.


Original source

Lin ZH, Xin YN, Dong QJ, et al. Performance of the aspartate aminotransferase-to-platelet ratio index for the staging of hepatitis C-related fibrosis: an updated meta-analysis. Hepatology. 2011; 53:726-36.


Khan DA, Fatima-Tuz-Zuhra, Khan FA, Mubarak A. Evaluation of diagnostic accuracy of APRI for prediction of fibrosis in hepatitis C patients. J Ayub Med Coll Abbottabad. 2008; 20(4):122-6.

Other references

1. Loaeza-del-Castillo A, Paz-Pineda F, Oviedo-Cárdenas E, Sánchez-Avila F, Vargas-Vorácková F. AST to platelet ratio index (APRI) for the noninvasive evaluation of liver fibrosis. Ann Hepatol. 2008; 7(4):350-7.

2. Sebastiani G, Halfon P, Castera L, Mangia A, Di Marco V, Pirisi M, Voiculescu M, Bourliere M, Alberti A. Comparison of three algorithms of non-invasive markers of fibrosis in chronic hepatitis C. Aliment Pharmacol Ther. 2012; 35(1):92-104.

Specialty: Hematology

Objective: Diagnosis

Type: Index

No. Of Variables: 3

Year Of Study: 2011

Abbreviation: APRI

Article By: Denise Nedea

Published On: June 6, 2017

Last Checked: June 6, 2017

Next Review: June 6, 2023