Page 2621 - Hematology_ Basic Principles and Practice ( PDFDrive )

e2 Part XIII Consultative Hematology

INTERPRETIVE COMMENTS

Complete Blood Count (Red Blood Cell) Parameters
Summary points • Used to identify anemia or polycythemia (RBC count, hemoglobin, hematocrit)
• RBC indices (MCV, MCH, MCHC, RDW) can characterize anemia according to RBC size and degrees of
hemoglobinization and anisopoikilocytosis
Methodology Automated hematology analyzer—flow cytometric or impedance methods
Specimen requirements Whole blood: EDTA
Indications Evaluation of anemia or polycythemia
Reference range Table 162.2
Interpretation • Anemia (low hemoglobin, hematocrit, RBC count)
• Microcytic, hypochromic: iron deficiency (often with high RDW), thalassemia (typically normal RDW but can be high,
high RBC count), sideroblastic anemia (may be dimorphic RBCs on peripheral smear), some cases of anemia of
chronic disease, hyperthyroidism
• Normocytic, normochromic: aplastic anemia, anemia of chronic disease, renal disease, hemolysis, bone marrow
infiltration, drugs, lead poisoning, myelodysplastic syndrome
• Macrocytic: vitamin B 12 or folate deficiency, liver disease, antimetabolite drugs, inherited bone marrow failure, some
cases of aplastic anemia, myelodysplastic syndrome, hemolysis with high reticulocyte count, hypothyroidism, alcohol
• Polycythemia (high hemoglobin, hematocrit)
• Primary: polycythemia vera, altered erythropoietin receptor
• Secondary: pulmonary disease, high-affinity hemoglobin, tumor related
Related tests • Peripheral smear review, reticulocyte count, bone marrow aspiration/biopsy, tests of renal and hepatic function,
hemoglobin fractionation/electrophoresis
• Microcytic, hypochromic anemias: iron studies, lead level (children), hemoglobin fractionation/electrophoresis
• Macrocytic anemias: vitamin B 12, folate, homocysteine, methylmalonic acid
• Normocytic anemias: markers of hemolysis (reticulocyte count, haptoglobin, indirect bilirubin, LDH)
• Polycythemia: family history, JAK2 mutation testing, erythropoietin level
Interfering substances Clotted or hemolyzed sample, cold agglutinin, lipemia, marked turbidity

EDTA, Ethylenediaminetetraacetic acid; MCH, mean corpuscular hemoglobin; MCHC, mean corpuscular hemoglobin concentration; MCV, mean corpuscular volume; RBC,
red blood cell; RDW, red blood cell distribution width.

Red Blood Cell Distribution Width

Summary points • Measures variability of red blood cell size (anisocytosis)
• Reported as either CV, SD, or both
Methodology Automated hematology analyzer
Specimen requirements Whole blood: EDTA
Indications Evaluation of anemia
Reference range RDW-CV: 11%–15% (based on adults) a
Interpretation • Elevated with increased variability in red blood cell size and shape; normal with more uniform, red blood cell size
• Hypochromic microcytic anemia
• Usually elevated with iron deficiency, hereditary sideroblastic anemia, thalassemia intermedia and major, and red
blood cell fragmentation
• Normal with anemia of chronic disease and thalassemia minor
• Normocytic or macrocytic anemia
• Usually elevated in folate or vitamin B 12 deficiency, mixed iron and folate or vitamin B 12 deficiency, some
hemoglobinopathies, myelofibrosis, acquired sideroblastic anemia, immune hemolytic anemia, and cold agglutinins
• Usually normal in anemia of chronic disease, some hemoglobinopathies, hemorrhage, hereditary spherocytosis,
and bone marrow failure
• RDW-CV = (SD of red cell volume/MCV)(100) reported more commonly than the RDW-SD
• RDW-SD less influenced by MCV and may be more accurate assessment of variability in red blood cell size
• Reference range will vary with the instrument used—check with laboratory
Related tests RBC, Hgb, Hct, MCV, MCH, MCHC, peripheral blood smear
Interfering substances Hemolyzed or clotted specimen
References Briggs C: Quality counts: New parameters in blood cell counting. Int J Lab Hematol 31:277, 2009.
a Evans TC, Jehle D: The red blood cell distribution width. J Emerg Med 9:71, 1991.

CV, Coefficient of variation; EDTA, ethylenediaminetetraacetic acid; Hgb, hemoglobin; Hct, hematocrit; MCH, mean corpuscular hemoglobin; MCHC, mean corpuscular
hemoglobin concentration; MCV, mean corpuscular volume; RBC, red blood cell count; RDW, red blood cell distribution width; SD, standard deviation.