A complete blood count (CBC) can indicate the diagnosis of acute leukemia. When acute leukemia occurs, a CBC often reveals anemia, typically normocytic normochromic anemia, and may show decreased platelet counts. The most noticeable changes are in white blood cell counts, which are frequently elevated. In some cases, white blood cell counts can exceed 100×10^9 per liter, though occasionally they may be decreased.
If a peripheral blood smear is performed, it often reveals the presence of immature leukemia cells, which strongly suggests a diagnosis of acute leukemia. In such cases, a bone marrow aspiration is necessary. The diagnosis of acute leukemia can be confirmed through bone marrow cytology and cytochemical staining.