Pathology Cheat Sheet
Count the Right White Cells
Leucocytosis for NEET-PG: neutrophilia and left shift, eosinophilia, basophilia, leukemoid reaction vs CML, LAP score, and leukoerythroblastic picture.
MedNext Academy | 3 min read
Count the Right White Cells
Leucocytosis for NEET-PG: neutrophilia and left shift, eosinophilia, basophilia, leukemoid reaction vs CML, LAP score, and leukoerythroblastic picture.
The patterns and causes of leucocytosis, distinguishing reactive responses from neoplastic proliferations.
High-yield lines
- Leucocytosis is a total white cell count above 11,000 per microlitre and is a finding rather than a diagnosis.
- Absolute counts, not percentages, must be used to interpret white cell changes.
- Neutrophilia occurs with acute bacterial infection, tissue necrosis, and corticosteroids.
- A left shift is the appearance of immature band forms and metamyelocytes in the blood during infection.
- Toxic granulation and Dohle bodies indicate reactive neutrophil activation in infection.
- Eosinophilia occurs in allergy, parasitic infestation, drug reactions, and some malignancies.
- Lymphocytosis occurs in viral infections such as infectious mononucleosis and in chronic lymphocytic leukaemia.
- Basophilia is uncommon and strongly suggests a myeloproliferative neoplasm such as chronic myeloid leukaemia.
- A leukemoid reaction is an extreme reactive neutrophilia that can mimic leukaemia.
- The leukocyte alkaline phosphatase score is high in a leukemoid reaction and low in chronic myeloid leukaemia.
- Chronic myeloid leukaemia is confirmed by the Philadelphia chromosome and BCR-ABL1 fusion, with prominent basophilia.
- A leukoerythroblastic picture with nucleated red cells and immature white cells suggests marrow infiltration.
Mapped competency codes
- PA18.1
Continue into the full chapter
This summary maps to PA18-leukocyte-disorders.
Frequently Asked Questions
How is a leukemoid reaction distinguished from chronic myeloid leukaemia?
A leukemoid reaction has a high leukocyte alkaline phosphatase score and is reactive, whereas chronic myeloid leukaemia has a low score, the Philadelphia chromosome, and basophilia.
Why must absolute counts be used to interpret white cell disorders?
Because a percentage can appear high simply because another cell line is depleted, so only absolute counts reflect the true number of each cell type.
What is a left shift?
The appearance of immature neutrophil precursors such as band forms and metamyelocytes in the peripheral blood, typically during bacterial infection.
What causes a leukoerythroblastic blood picture?
Bone marrow infiltration or fibrosis, which pushes immature white cells and nucleated red cells into the circulation.
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