CBC with retic count
Decrease from baseline hemoglobin/hematocrit
Precipitous drop in reticulocyte count (or lack of response)
Decrease from baseline hemoglobin/hematocrit
Precipitous drop in reticulocyte count (or lack of response)
Aplastic crisis
Tumor lysis syndrome
Sickle cell crisis
Immune reconstitution syndrome
Acute transfusion reaction
Leukemia 
Leukemia
Acute myeloid leukemia