This slide shows a LAP stain of a blood smear from a normal person. The segmented neutrophil in the center of the field is negative for alkaline phosphatase; it would be scored a 0 and the cell containing red granules on the right scored a 3. The criteria for scoring depend on the size of the granules, the staining intensity, and the background color of the cytoplasm. The LAP is the single most useful laboratory test for differentiating CML from leukemoid reaction. The score in CML varies from 0 to 10, and in leukemoid reaction it is usually greater than normal (normal, 11-130). The score is obtained by counting a total of 100 segmented neutrophils and band forms, scoring the amount of LAP in each on a scale from 0 to 4, and then adding the individual scores for the total. The lowest possible score is 0 and the highest possible is 400. Only segmented neutrophils and band forms contain LAP, and they must be identified for positivity. All other cell types are ignored.
Course Section: 08. Myelocytic Leukemia: Chronic and Acute
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