Leukocyte Alkaline Phosphatase Stain (LAP)

LAP Procedure—an Inexact Science!

September 2010

The LAP assay is clearly a subjective test based on an inexact science. The procedure involves counting 100 neutrophils including lobed and band forms but excluding other left-shifted granulocytes, eosinophils, and basophils. The reaction is scored from 0 to 4 depending on the number of stained granules and the intensity of the stain. The number of cells is multiplied by the score and added up with a normal range being from 40 to 100.

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Jump to section:

• Introduction
• Optimizing Laboratory Testing for Hematologic Disorders Series
• The Big Picture: We Need to Focus On...
• LAP: A Test That Time Has Passed By
• Abbreviations
• LAP: Assay History
• LAP: Original Clinical Utility
• LAP Procedure—an Inexact Science!
• Typical Staining Type Reaction
• Subjective Nature of the Scoring Process
• LAP Scoring Example
• LAP Discontinued at Mayo Clinic
• Low LAP Scores* Not Specific for CML: A Mayo 1-Year Experience
• Low LAP Scores* Do Not Indicate Myeloid Malignancy: A Mayo 1-Year Experience
• High LAP Scores* Not Specific for PV: A Mayo 1-Year Experience
• High LAP Scores* Do Not Indicate Myeloid Malignancy: A Mayo 1-Year Experience
• LAP: A Test Whose Time Has Passed
• Consequences of an Abnormal LAP
• Alternatives to LAP
• Alternatives to LAP: BCR/ABL
• Alternatives to LAP: JAK2
• Conclusions
• Questions?