Use
AST to Platelet Ratio Index (APRI) is reported to be a simple, noninvasive, and readily available laboratory test index that can stratify patients with HCV and Non-Alcoholic Fatty Liver Disease (NAFLD) who are at high or low risk for significant fibrosis and cirrhosis with high degree of accuracy.

Limitations
Clumping may cause false low count. Platelet satellitism around neutrophils will cause a pseudothrombocytopenia. RBC or WBC fragments including fragmented fragile leucemic cells and neutrophil pseudoplatelets may cause falsely elevated counts.

Methodology
AST: kinetic; Platelet Count: automated cell counter