Neutrophil Alkaline Phosphatase (NAP)

leukocyte alkaline phosphatase (LAP) the isozyme of alkaline phosphatase occurring in the leukocytes, specifically in the neutrophils; LAP activity is used in the differential diagnosis of neutrophilia, being lowered in chronic myelogenous leukemia but elevated in a variety of other disorders.

an enzyme present in lymphocytes that is elevated in various diseases such as cirrhosis and polycythemia and in certain infections. It is measured in the blood to detect these disorders and to differentiate chronic myelogenous (myelocytic) leukemia from leukemoid reactions. Normal amounts of this enzyme in a smear of fresh venous blood are 50 to 150 units. Also called neutrophil alkaline phosphatase. the low level of neutrophil alkaline phosphatase in CML granulocytes is the result of decreased enzyme content and not a consequence of synthesis of catalytically defective enzyme.