Hi, I don't know the answer -- but since both CML and Gleevec toxicity produce anemia because of marrow suppression, maybe it's not possible to tell the difference. E.g., both would show a low reticulocyte count.
This full text paper on anemia from Gleevec https://onlinelibrary.wiley.com/doi/full/10.1002/ajh.23879 shows that other signs such as red blood cell size can vary, so that doesn't seem to help. Sorry.