Age, severe aplastic anemia, CYP2C19 poor metabolizer (CYP2C19*2/*2, *2/*3, or *3/*3), PPIs (omeprazole/lansoprazole/pantoprazole/esomeprazole), CYP2C19 poor metabolizer/PPIs use combination. This evidence concerns the gene CYP2C19 and aplastic anemia.