Patients with leukemia usually undergo a complete blood count (CBC) test. Conducting a CBC test is one of the most basic examination methods. When leukemia occurs, anemia may be detected in the CBC results. In the case of patients with acute leukemia, a decrease in platelets may also be observed in the CBC. In most cases, an increase in the white blood cell count can be seen, while in a few cases, a decrease in white blood cells may occur. If chronic leukemia develops, the platelet count in the CBC may be normal or increased in the early stage, and the white blood cell count can also show a significant increase. The difference lies in the results of a peripheral blood smear test between acute leukemia and chronic leukemia. In acute leukemia, primitive leukemia cells can be found in the peripheral blood smear. In chronic myeloid leukemia, immature granulocytes at various stages can be detected in the peripheral blood smear. In chronic lymphocytic leukemia, an increase in mature small lymphocytes can be found in the peripheral blood smear.