Complete Blood Count (CBC) With Differential

A six-part differential reported in some lab locations includes IG % and IG absolute counts. IG (immature granulocytes) includes metamyelocytes and myelocytes. It does not include bands or blast cells.^1,2 Promyelocytes and blasts are reported separately to denote the degree of left shift. An elevated percentage of IG has not been found to be clinically significant as a sole clinical predictor of disease. IGs are associated with infections, a variety of inflammatory disorders, cytokine therapy, neoplasia, hemolysis, tissue damage, seizures, metabolic abnormalities, myeloproliferative neoplasms, and with the use of certain medications such as steroids.³

Pregnancy-associated leukocytosis may also show increased immature granulocytes without clinical significance. There is a significant increase of normoblastic erythropoiesis and, to a lesser extent, of granulopoiesis during pregnancy, which is associated with an increase in immature cells (shift to the left) of both erythropoietic and granulopoietic tissues. A possible physiologic explanation for the appearance of immature granulocytes in the peripheral blood of pregnant women, increased alkaline phosphate activity in granulocytes, and increased glycogen content of lymphocytes may be found in the excretion curves of hormones during pregnancy. There is a sharp rise in the fifth month then a decrease in the eighth month and a subsequent rise in the ninth month.⁴

3. CAP Today. August 2010, Q&A Section.

4. Efrati P, Presentey B, Marglaith M, Rozenszajn L. Leukocytes of normal pregnant women. Obstet Gynecol. 1964 Mar; 23:431-432.PubMed 14128474