05/09/2025
π¬ Left Shift in Hematology
Definition
β’ A left shift means an increase in immature neutrophils in peripheral blood.
β’ Normally, circulating neutrophils are mostly segmented (mature) forms.
β’ When the demand for neutrophils is high (infection, inflammation, marrow stimulation), the bone marrow releases earlier precursors (bands, metamyelocytes, and sometimes myelocytes).
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Normal Distribution of Neutrophils
β’ Segmented neutrophils (segs): 40β70% of circulating WBCs
β’ Bands: 0β5% of circulating WBCs
β’ Metamyelocytes & myelocytes: not normally seen in peripheral blood (except in severe stress, marrow disease, or myeloproliferative states)
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π¨ Left Shift Criteria
β’ Bands > 10% of total WBCs
OR
β’ Immature granulocytes (bands + metamyelocytes + myelocytes) > 1,000/Β΅L absolute count
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π Causes of Left Shift
1. Infections (bacterial sepsis, pneumonia, abscess)
2. Inflammation (tissue injury, burns, myocardial infarction)
3. Bone marrow stimulation (growth factor therapy, recovery after chemotherapy)
4. Myeloproliferative neoplasms (CML, leukemoid reaction)
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π Clinical Significance
β’ A mild left shift (β bands only) β often bacterial infection.
β’ A marked left shift (bands + metamyelocytes + myelocytes in blood) β severe infection, sepsis, or bone marrow stress.
β’ Presence of toxic changes (toxic granulation, DΓΆhle bodies, cytoplasmic vacuoles) with a left shift further supports acute bacterial infection.
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βοΈ Key Point on Bands
β’ Normal: β€ 5% of neutrophils
β’ Left shift: > 10% bands, or bands present along with earlier precursors
β’ Example: WBC 20,000/Β΅L with 20% bands = absolute band count 4,000/Β΅L β significant left shift
