<prompt> The difference between leukemia and leukemoid reaction is done by -Leukocyte alkaline phosphataseImmature cellsTotal leukocyte countE.S.R.  <response>: Leukemoid reaction is defined as a reactive excessive leukocytosis in peripheral blood resembling that of leukemia in a subject who doesnot have leukemia. Leucocyte alkaline phosphatase LAP score in the cytoplasm of mature neutrophils is high in leukaemoid reaction whereas reduced in CML .It is very useful to distinguish between the two. Reference; Harsh Mohan textbook of pathology, 7th edition.Pg no.332 