Evaluation of Leukocytosis: The term 'leukocyte' applies to any cells within the myeloblast, monoblast, & lymphoid lineages. Include granulocytes (neutrophils, eosinophils, & basophils), monocytes, & lymphocytes (B cells, T cells, and natural killer cells). In adults, leukocytosis often defined as white blood cell (WBC) count > 11 × 109/L. Mature WBC: 80-90% remain in storage in bone marrow. 2% to 3% circulate freely in peripheral blood; The rest stay deposited along the margins of blood vessel walls or in the spleen Life span: 2- 16 days (depending on cell type in the peripheral circulation). LEUCOCYTOSIS WBC > 11,000 per mm3 [11.0 × 109 per L] Reactive: Typically, 11,000 to 30,000 per mm3. Leukemoid reaction: approx. 50,000-100,000 per (e.g., C difficile infection, sepsis, organ rejection, or solid tumors. Leukemias or myeloproliferative disorders: > 100,000 per mm3. Paradoxical neutropenia: typhoid fever, rickettsia infections, brucellosis, & dengue. Neutrophil bands: Immature neutrophils Morphologically: absence of complete separation of nuclear lobes with a visible distinction between chromatin & parachromatin in the narrowest segment of the nucleus often flagged on 5-part automated differential & confirmed by PBS. Leukemoid Reaction: Transient increase in WBC count defined as significant neutrophilia >50x10^9/L in the absence of a myeloproliferative neoplasm. Mature neutrophils seen in a leukemoid reaction. Etiology: sepsis, organ rejection, solid tumors, and bacterial infections. D/D leukemia: increases in blast cells (precursor cells to leukocytes) and immature WBCs, Improves after treating the underlying cause. #LEUCOCYTOSIS #LEUKEMOIDREACTION #BANDS #NEUTROPHILS #WCC #BASOPHILS
