Answer: From my experience... It depends on what type of white blood cells is elevated. A WBC (white blood count) that is elevated shows a presence of infection. Where as when your BLAST count (or immature white blood count) is elevated, that is what shows the presence of leukemia.
Explanation: My brother had something called Meiloproliferative disorder of an infant, which is also called acute leukemia. This is how the doctors explained it to me.