A peripheral blood smear cannot completely rule out leukemia, and a bone marrow aspiration is required to confirm a diagnosis of leukemia. A peripheral blood smear is one of the most useful tests for hematologic disorders, allowing for special staining of the blood smear and also identifying leukemia, infections, and other diseases. Peripheral blood smears can detect some patients with leukemia, but are not a diagnostic criterion. The presence of primitive as well as naïve leukemia cells in the blood smear can indicate leukemia, but leukemia cannot be completely ruled out when the blood smear is completely normal. Because some leukemia patients have normal blood smears, such as hypoproliferative leukemia, the number of cells in the blood smear is small, sometimes there may be no leukemia cells, at this time can not be completely excluded leukemia. Therefore, clinically, it is generally not possible to exclude leukemia with blood smear, but it is necessary to exclude it through routine examination of bone marrow. Specific diagnosis should be made under the guidance of a physician.