Activity 4B. Calculating APRI
A 61-year-old man with a recent diagnosis of hepatitis C infection is seen in the clinic for follow-up after an initial visit. His initial laboratory studies show the following:
- Total bilirubin = 1.6 mg/dL
- Aspartate aminotransferase (AST) level = 120 IU/L (upper limit of normal for men = 40 IU/L)
- Platelet count = 100 x 109/L
- Albumin = 3.4 g/dL
Instructions
- Using the APRI Calculator tool, enter in the patient’s laboratory data and calculate the patient’s APRI score.
- Answer the Activity Question based on the patient’s APRI score.
AST to Platelet Ratio Index (APRI) Calculator
This is an AST to Platelet Ratio Index (APRI) calculator tool. Enter the required values to calculate the APRI value. The APRI Score will appear in the oval on the far right (highlighted in yellow). Most experts recommend using 40 IU/L as the value for the AST upper limit of normal when calculating an APRI value.
APRI =
AST Level (IU/L)
AST (Upper Limit of Normal) (IU/L)
Platelet Count (109/L)
x 100 =
3.000
Interpretation:
In a meta-analysis of 40 studies, investigators concluded that an APRI score greater than 1.0 had a sensitivity of 76% and specificity of 72% for predicting cirrhosis. In addition, they concluded that APRI score greater than 0.7 had a sensitivity of 77% and specificity of 72% for predicting significant hepatic fibrosis.1For detection of cirrhosis, using an APRI cutoff score of 2.0 was more specific (91%) but less sensitive (46%). The lower the APRI score (less than 0.5), the greater the negative predictive value (and ability to rule out cirrhosis) and the higher the value (greater than 1.5) the greater the positive predictive value (and ability to rule in cirrhosis); midrange values are less helpful. The APRI alone is likely not sufficiently sensitive to rule out significant disease. Some evidence suggests that the use of multiple indices in combination (such as APRI plus FibroTest) or an algorithmic approach may result in higher diagnostic accuracy than using APRI alone.2