About the APRI Score Calculator
The AST to Platelet Ratio Index (APRI) is a simple blood-test score for estimating liver fibrosis without a biopsy. It combines two changes that happen as the liver scars: aspartate aminotransferase (AST) tends to rise, and the platelet count falls as portal hypertension and reduced thrombopoietin develop. Dividing one by the other amplifies both signals into a single number.
Enter the AST result, the upper limit of normal (ULN) for AST used by the laboratory that ran the test, and the platelet count in 10⁹/L (the same as thousands per microlitre). The calculator returns the APRI and classifies it against the two pairs of cut-offs from the original study by Wai and colleagues: 0.5 and 1.5 for significant fibrosis, and 1.0 and 2.0 for cirrhosis. Values between each pair are indeterminate.
APRI was developed and validated in 270 consecutive treatment-naive patients with chronic hepatitis C who had a liver biopsy (a training set of 192 and a validation set of 78). It has since been used in other chronic liver diseases, where its accuracy is lower. It is best at ruling fibrosis in or out at the extremes, and results in the middle range usually need elastography or another test. It does not diagnose the cause of liver disease.
With the default inputs, the apri is 1.33. Change any value above to recalculate instantly.
How to use the apri score calculator
- 1Enter the AST value from a recent liver panel.
- 2Enter the AST upper limit of normal printed on the lab report.
- 3Enter the platelet count from a blood count taken around the same time.
- 4Read the APRI and how it compares with the fibrosis and cirrhosis cut-offs.
Formula and method
AST is expressed as a multiple of the laboratory’s upper limit of normal so that results are comparable between laboratories, then divided by the platelet count in 10⁹/L and multiplied by 100. Higher values mean more fibrosis is likely.
In the derivation study, an APRI of 0.5 or less made significant fibrosis (Ishak stage 3 or more) unlikely, and more than 1.5 made it likely. For cirrhosis, 1.0 or less made it unlikely and more than 2.0 made it likely. Using these optimised cut-offs, significant fibrosis could be predicted accurately in about half of patients and cirrhosis in about four in five.
- AST
- Aspartate aminotransferase (U/L)
- ULN
- Laboratory upper limit of normal for AST (U/L)
- Platelets
- Platelet count in 10⁹/L (thousands per µL)
Worked examples
Indeterminate result
AST 80 is 2.0 × the ULN of 40. Dividing by a platelet count of 150 and multiplying by 100 gives APRI ≈ 1.33, which is between both pairs of cut-offs, so further testing would be needed.
Low APRI
30 ÷ 40 = 0.75; 0.75 ÷ 250 × 100 = 0.30. This is below 0.5, so significant fibrosis and cirrhosis are both unlikely by APRI.
High APRI with low platelets
AST is 120 ÷ 35 ≈ 3.43 × ULN; divided by 90 and multiplied by 100 gives APRI ≈ 3.81. This exceeds 2.0, the cut-off at which cirrhosis is likely.
Frequently asked questions
What is a normal APRI score?+
There is no single normal value, but an APRI of 0.5 or below makes significant liver fibrosis unlikely in chronic hepatitis C, and 1.0 or below makes cirrhosis unlikely according to the original Wai cut-offs.
What APRI score indicates cirrhosis?+
In the derivation study an APRI above 2.0 made cirrhosis likely. Values between 1.0 and 2.0 are indeterminate. The World Health Organization has also used an APRI above 2 to identify likely cirrhosis in hepatitis C programmes.
How accurate is APRI?+
APRI is good at the extremes but misses or overcalls fibrosis in the middle range. It was developed in hepatitis C; accuracy is lower in hepatitis B, fatty liver disease and alcohol-related liver disease, where FIB-4 or elastography is often preferred.
What units should the platelet count be in?+
Use 10⁹/L, which is numerically the same as thousands per microlitre (for example 150,000/µL = 150 × 10⁹/L). Entering the raw count (150,000) would make APRI 1,000 times too small.
How is APRI different from FIB-4?+
FIB-4 adds age and ALT to AST and platelets. Both are free, simple scores; FIB-4 is more widely recommended for fatty liver disease, while APRI was designed for chronic hepatitis C.
For healthcare professionals and education only. This calculator implements a published formula or score but is not a diagnosis and does not replace clinical judgment. Verify inputs and results against the original source before using them in patient care.