Leukocyte Alkaline Phosphatase (LAP/NAP score) in peripheral blood smear (human)

Stain: Alkaline phosphatase staining (Ackerman). In mature neutrophils granules contain alkaline phosphatase. In eosinophils no alkaline phosphatase activity is present. A considerable number of brown stained neutrophils can be indicative for a patient with infection (leukemoid reaction, A). Image in (B) is from a patient with CML (chronic myeloid leukaemia) showing an increased number of leucocytes without toxic granules, i.e., alkaline phosphatase-negative. Cytochemical reactions in smears are useful for the differential diagnosis of certain diseases.