- An elevated WBC count with mainly neutrophils suggests inflammation or infection.
- A very high WBC count (>50,000) that is not a leukemia is known as a “leukemoid reaction”.
- This reaction can be distinguished from malignant WBC’s by the presence of large amounts of leukocyte alkaline phosphatase (LAP) in the normal neutrophils.
Neutrophilia – leukemoid reaction
- LAP is an enzyme present in normal neutrophils, but absent (or present at very low concentrations) in malignant neutrophils (i.e., the ones in CML)
- the LAP is strongly positive in cell image below, you can be quite sure that it is a benign neutrophil
Benign Neutrophil – High LAP activity
- if the LAP is negative, or weakly positive, as in the image below, that probably means that those neutrophils are malignant and that you’re dealing with a case of CML
- Malignant Neutrophil – Low LAP Activity
Sources & References: pathologystudent.com library.med.utah.edu
