The RDW can also be high after recent hemorrhage or rapid hemolysis, as the acute drop in hemoglobin results in increased production of reticulocytes, which are larger than mature erythrocytes.īecause a range of disorders can elevate the RDW, reviewing the peripheral blood smear is an important next step in the diagnostic evaluation, specifically looking for reticulocytes, microspherocytes, and other abnormal red blood cells contributing to the RDW elevation.Ī normal RDW is less diagnostically useful. 1 In iron deficiency, the RDW often rises before the mean corpuscular volume falls, serving as an early diagnostic clue. This information is helpful in differentiating the cause of microcytic anemia, as a high RDW suggests iron-deficiency anemia while a normal RDW suggests thalassemia. The RDW can differentiate between causes of anemiaĪ high RDW is often found in nutritional deficiencies of iron, vitamin B 12, and folate. By incorporating an awareness of their value in clinical practice, providers can maximize the usefulness of the CBC. In addition to describing their diagnostic utility, we also discuss emerging evidence of their potential prognostic significance in hematologic and nonhematologic disorders. The nucleated red blood cell (NRBC) count. The red blood cell distribution width (RDW) For example, the absolute neutrophil count is an important measure of immunocompetence.īut other values in the CBC may be overlooked, even though they can provide important information. The differential white blood cell count provides absolute counts and relative percentages of each type of leukocyte. Providers use it to classify anemia as either microcytic, normocytic, or macrocytic, each with its own differential diagnosis. The mean corpuscular volume is the average volume of red blood cells. Now, with automated counters, the CBC report also contains other numbers that delineate characteristics of each cell type. These 3 numbers are still the primary purpose of the test. Not long ago, the CBC required peering through a microscope and counting the red blood cells, white blood cells, and platelets. T he complete blood cell count (CBC) is one of the most frequently ordered laboratory tests in both the inpatient and outpatient settings. It can also indicate a serious underlying hematologic disorder. Furthermore, emerging evidence suggests that high MPV is associated with worse outcomes in cardiovascular disorders.Īn elevated NRBC count may predict poor outcomes in a number of critical care settings. The MPV can be used in the evaluation of thrombocytopenia. Studies also suggest that a high RDW may be associated with an increased rate of all-cause mortality and may predict a poor prognosis in several cardiac diseases. The RDW can help differentiate the cause of anemia: eg, a high RDW suggests iron-deficiency anemia, while a normal RDW suggests thalassemia.
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