Reactive Left Shift

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A relative left shift in the granulocyte series means less mature forms in excess of 5% band neutrophils; the preceding, less differentiated cell forms are included and all transitional forms are taken into account. This left shift almost always indicates an increase in new cell production in this cell series. In most cases, it is associated with a raised total leukocyte count. However, since total leukocyte counts are subject to various interfering factors that can also alter the cell distribution, left shift without leukocytosis can occur, and has no further diagnostic value. At best, if no other explanations offer, a left shift without leukemia can prompt investigation for splenomegaly, which would have prevented elevation of the leukocyte count by increased sequestration of leukocytes as in hypersplenism.

In evaluating the magnitude of a left shift, the basic principle is that the more immature the cell forms, the more rarely they appear; and that there is a continuum starting from segmented granulocytes and sometimes reaching as far as myeloblasts. Accordingly, a moderate left shift of medium magnitude may include myelocytes and a severe left shift may go as far as a few promyelocytes and (very rarely) myeloblasts, all depending on how fulminant the triggering process is and how responsive the individual. The term "pathological left shift" (for a left shift that includes promyelocytes and myeloblasts) is inappropriate, because such observations can reflect a very active physiological reaction, perhaps following a "leukemoid reaction" with pronounced left shift and leukocytosis.

Causes of Reactive Left Shift

Left shift occurs regularly in the following situations:

> Bacterial infections (including miliary tuberculosis),

> Nonbacterial inflammation (e.g., colitis, pancreatitis, phlebitis, and connective tissue diseases)

> Cell breakdown (e.g., burns, liver failure, hemolysis)

Left shift sometimes occurs in the following situations:

> Infection with fungi, mycoplasm, viruses, or parasites

> Myocardial or pulmonary infarction

> Metabolic changes (e.g., pregnancy, acidosis, hyperthyroidism)

> Phases of compensation and recuperation (hemorrhages, hemoly-sis, or after medical or radiological immunosuppression).

Predominance of the granulocytic lineage with copious granulation and sporadic immature cells: usually a reactive left shift a c

Hematology Shift Left

Fig. 38 Left shift. a and b Typical blood smear after bacterial infection: toxic granulation in a segmented granulocyte (1), monocyte with gray-blue cytoplasm (2), metamyelocyte (3), and myelocyte (4). c Blood analysis in sepsis: promyelocyte (1) and orthochromatic erythroblast (2). Thrombocytopenia. d and e Reactive left shift as far as promyelocytes (1). Particularly striking are the reddish granules in a band neutrophilic granulocyte (2).

Fig. 38 Left shift. a and b Typical blood smear after bacterial infection: toxic granulation in a segmented granulocyte (1), monocyte with gray-blue cytoplasm (2), metamyelocyte (3), and myelocyte (4). c Blood analysis in sepsis: promyelocyte (1) and orthochromatic erythroblast (2). Thrombocytopenia. d and e Reactive left shift as far as promyelocytes (1). Particularly striking are the reddish granules in a band neutrophilic granulocyte (2).

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Responses

  • Matilda
    Where can one find left shift in leukaemia?
    2 years ago
  • david
    What does blood work with reactive left shift mean?
    1 year ago

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