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.
