Neutrophil alkaline phosphatase, abbreviated as NAP, is an enzyme present in mature granulocytes, commonly found in rod nucleated granulocytes and lobulated nucleated granulocytes, in other cells, there is no presence of this enzyme, because of this, clinically it can be proved by special staining, as long as the detection of this enzyme can prove the existence of rod nucleated granulocytes and lobulated nucleated granulocytes. Clinically, it is often used in the diagnosis of acute leukemia types, such as acute granulocytic leukemia patients, neutrophil alkaline phosphatase is strongly positive, while in acute monocytic leukemia, neutrophil alkaline phosphatase is weakly positive, but in acute lymphoblastic leukemia, neutrophil alkaline phosphatase is negative. In addition, for the differential diagnosis of leukocytosis in the peripheral blood, neutrophil alkaline phosphatase is strongly positive in patients with a leukemia-like reaction or an acute infection-induced increase in neutrophil counts, but is negative in patients with chronic granulocytic leukemia.