Complete Blood Count (CBC) With Differential

Overview:

As a screening test to evaluate overall health; detect and/or identify a wide range of hematologic disorders; assist in managing medications/chemotherapeutic decisions.

Assessments of stained smears are performed if results meet specific numeric and/or instrument flagging criteria. Smear review includes assessment of WBC cell populations, presence of WBC and/or RBC inclusions, RBC morphology, and platelet evaluation.

Presence of one or more of the following may be indication for further investigation: hemoglobin <10 g/dL, hemoglobin >18 g/dL, MCV >100 fL, MCV <80 fL, MCHC >37%, WBC >20,000/mm3, WBC <2000/mm3, presence of sickle cells, spherocytes, Pappenheimer bodies, basophilic stippling, stomatocytes, schistocytes (fragmented RBCs), target cells, oval macrocytes, teardrop red blood cells, abnormal cell populations, nucleated red blood cells in other than the newborn, blood parasites (malarial or Babesia organisms or the possibility of parasitic organisms), hypersegmented neutrophils, agranular neutrophils, hyposegmented neutrophils (Pelger-Huët anomaly or pseudo-Pelger-Huët [pelgeroid] cells), mononuclear cells in which apparent nucleoli are prominent (blast-like cells), presence of metamyelocytes, myelocytes, promyelocytes, neutropenia, presence of plasma cells, peculiar atypical lymphocytes, significant increase or decrease in platelets or bizarre platelets.

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

1. Fernandes B, Hamaguchi Y. Automated enumeration of immature granulocytes. Am J Clin Path. 2007 Sep; 128(3):454-463. PubMed 17709320

2. Ansari-Lari M, Kickler TS, Borowitz MJ. Immature granulocyte measurement using the Sysmex XE-2100. Relationship to infection and sepsis. Am J Clin Pathol. 2005 Nov; 120(5):795-799. PubMed 14608908

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