Test Details: This test is used to measure the amount of alkaline phosphatase, a group of enzymes, in certain white blood cells. Before the advent of more advanced tests, the LAP test was commonly used to diagnose chronic myeloid leukemia (CML). The LAP score is derived by counting one hundred neutrophils (and/or bands) and assessing the amount of stain retained in each of these neutrophilic cells. Each cell is assigned a score between 0 (no stain retained) to 4 (very dark staining due to the granules retaining the stain).