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In the study in which the APRI score was developed, the score correctly predicted significant scarring of the liver in 51% of patients. It correctly predicted advanced scarring in 81%.[1]
On this page you can read what the APRI score is, what the guidelines say about a value that is too low or too high, what affects your value and which values are best to look at alongside it.
Also known as: AST to platelet ratio index, AST-to-platelet ratio. At the lab: n/a.
APRI stands for AST to platelet ratio index. It is the ratio between AST (aspartate aminotransferase) and the number of platelets in your blood.[1]
Researchers at the University of Michigan described the index in 2003. They were looking for a simple model using common lab values.[1]
Scarring of the liver has an opposite effect on AST and on the platelet count. The APRI score was designed to amplify that difference.[1]
With long-term inflammation of the liver caused by a virus, it is important to know how far the scarring has progressed. That information is essential for care.[1]
Most models for estimating scarring are complicated and need separate formulas. The APRI score does it with a single, simple calculation.[1]
The researchers tested the score in patients who had a liver biopsy: 192 in the first group and 78 in the control group.[1]
In the control group, the AUC, a measure of how well the score tells groups apart, was 0.88 for significant and 0.94 for advanced scarring.[1]
| Level | Can point to | Who it is for |
|---|---|---|
| Above the cut-off value for significant scarring[1] | Significant scarring of the liver | Patients with long-term inflammation of the liver caused by a virus |
| Above the cut-off value for advanced scarring[1] | Advanced scarring of the liver | Patients with long-term inflammation of the liver caused by a virus |
Source: Wai et al., Hepatology. Applies to patients with long-term inflammation of the liver caused by a virus. The abstract gives no figure for the cut-off values.[1]
A score above the cut-off value can point to significant or advanced scarring of the liver. It is still an estimate. In the study, the prediction was correct in 51% and in 81% of patients.[1]
BioProfile is working on its own zones for each value, from risk to optimal. A doctor reviews those zones before they appear in your result.
The score is the ratio between AST and the platelet count. With the same platelet count, a higher AST gives a higher score.[1]
Because the platelets sit at the bottom of the ratio, fewer platelets with the same AST actually give a higher score.[1]
According to the researchers, scarring of the liver has an opposite effect on AST and on the platelet count. The index was designed to amplify that effect.[1]
The APRI score is included in BioProfile 77, 87, 121 and 150.[2]
The BioProfile editorial team wrote this page on 26 October 2026 from the sources below, which we read on 26 October 2026. Every number on this page comes from one of those sources, with that source's number next to it. An expert has yet to check this page; once that check is done, the expert's name and the date of the check will appear at the top. This page explains and does not diagnose. Discuss an abnormal value with your GP.
