APRI Calculator

Created by Joanna Michałowska, PhD candidate
Reviewed by Dominik Czernia, PhD and Jack Bowater
Last updated: Oct 18, 2022

The APRI calculator computes the AST to Platelet Ratio Index (APRI), which we use to predict fibrosis and cirrhosis. Calculating a patient's APRI score allows clinicians to easily predict hepatic fibrosis without performing a more invasive medical tests, e.g., biopsy.

Are you interested in other calculators that can help assess whether or not a patient has liver disease? Check out the MELD calculator (Model for End-Stage Liver Disease) and the Child Pugh calculator.

We try our best to make our Omni Calculators as precise and reliable as possible. However, this tool can never replace a professional doctor's assessment.

AST to Platelet Ratio Index - How to calculate APRI score?

The aspartate aminotransferase (AST) to platelet ratio index is an easy, non-invasive alternative to liver biopsy for identifying hepatic fibrosis. Currently, a biopsy is the most common method for diagnosing liver fibrosis. However, this procedure is associated with patient discomfort and, in some cases, complications.

Therefore, researchers developed APRI, an indirect biochemical marker of hepatic fibrosis. We calculate it using routine laboratory parameters, which reflect alterations in hepatic function. It was initially validated in patients with chronic hepatitis C (CHC), but can also be used to identify other common fibrotic liver diseases.

The formula used to calculate APRI is:

APRI = [(AST level / AST upper limit) / Platelet count] × 100

where,

AST level - the aspartate aminotransferase level of the patient, expressed in IU/L (international units per litre);

AST upper limit - a value used to make the calculations more specific. Most experts recommend using the value of 40, expressed in IU/L; and

Platelet count - the patient's platelet count, expressed in 10⁹/L.

APRI score - interpretation

We can interpret the APRI score as follows:

  • Significant fibrosis: APRI threshold of 0.7 (77% sensitive and 72% specific);

  • Severe fibrosis: APRI threshold of 1.0 (61% sensitive and 64% specific); and

  • Cirrhosis: APRI threshold of 1.0 (76% sensitive and 72% specific).

The percentages above are the correlation coefficients:

*Sensitivity - ability to correctly identify those with the disease (true positive rate).

*Specificity - ability to correctly identify those without the disease (true negative rate).

The results are based on the study Performance of the Aspartate Aminotransferase-To-Platelet Ratio Index for the Staging of Hepatitis C-related Fibrosis: An Updated Meta-Analysis.

The interpretation is based on another systematic review, Blood Tests to Diagnose Fibrosis or Cirrhosis in Patients With Chronic Hepatitis C Virus Infection:

  • a low APRI score (less than 0.5) is associated with a greater negative predictive value (and the ability to rule out cirrhosis); and

  • a high APRI score (greater than 1.5) is associated with a greater positive predictive value (and the ability to rule in cirrhosis).

The APRI calculator

To find out the patient's APRI score, you need to enter only two values:

  1. AST level - the aspartate aminotransferase level of the patient (expressed in IU/L, i.e., international units per litre).

  2. Platelet count - the patient's platelet count (expressed in 10⁹/L).

The third value, AST upper limit, is optional. It is, by default, 40 IU/L, but you can change if you need.

Calculating APRI score - a practical example

Let's calculate the APRI score of a patient with the following laboratory tests:

  • AST level - 110 IU/L;
  • AST upper limit - 40 IU/L; and
  • platelet count - 110 × 10⁹/L.

APRI = [(AST level / AST upper limit) / Platelet count] × 100

APRI = [(110 / 40) / 110] × 100

APRI = [2.75 / 110] × 100

APRI = 0.025 × 100

APRI = 2.5

This patient likely has severe fibrosis or cirrhosis.

Joanna Michałowska, PhD candidate
AST level
IU/L
AST upper limit
IU/L
Platelet count
⋅10⁹/L
AST to Platelet Ratio Index
APRI score
APRI score interpretation:

▪️ Significant fibrosis: APRI threshold of 0.7 (77% sensitive and 72% specific);

▪️ Severe fibrosis: APRI threshold of 1.0 (61% sensitive and 64% specific); and

▪️ Cirrhosis: APRI threshold of 1.0 (76% sensitive and 72% specific).

There are no universal cut-off values for the APRI score, as it is not sufficiently sensitive to rule out significant diseases (especially with midrange values). The lower the APRI score (<0.5), the greater the negative predictive value, and ability to rule out cirrhosis. The higher the value (>1.5) the greater the positive predictive value and ability to rule in cirrhosis.

Check out 56 similar general health calculators ⚕️
20/20 Vision for 2020Acid-baseAlvarado score… 53 more
People also viewed…

Chilled drink

With the chilled drink calculator you can quickly check how long you need to keep your drink in the fridge or another cold place to have it at its optimal temperature. You can follow how the temperature changes with time with our interactive graph.

Flat vs. round Earth

Omni's not-flat Earth calculator helps you perform three experiments that prove the world is round.

Maintenance fluids for children

Maintenance fluids calculator determines the daily and hourly amount of water needed for a child of a given weight.

Vital capacity

The vital capacity calculator estimates your respiratory volume using age, sex, and height.
Copyright by Omni Calculator sp. z o.o.
Privacy policy & cookies
main background