Leucocyte alkaline phosphatase (LAP) is raised in all conditions except:
Myelofibrosis
Essential thrombocythemia
Chronic myeloid leukaemia
Polycythemia
Low LAP scores have been associated with CML, PNH, thrombocytopenic purpura, and hereditary hypophosphatasia. In CML regardless of the total white count, the score remains low.
Chronic Myelogenous Leukemia