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Lesson 9-2
Laboratory Assessment of Anemia

INTRODUCTION

To determine or detect the presence of anemia, the clinical laboratory professional performs a complete blood count on a hematology cell analyzer to determine the RBC count, hemoglobin, hematocrit, RBC indices, white blood cell count, and platelet count. In this section practice questions will be provided to reiterate how to calculate and interpret the usages of RBC indices in diagnosing anemia.

Calculate the RBC indices

  1. A patient was treated in the Emergency Room for severe lacerations and possible abdominal injuries as a result of an automobile accident. Results of the initial CBC were:

  1. A patient's CBC results were:


LABORATORY EVALUATIONS/PROCEDURES

Red cell distribution width (RDW).

  • Indicates the degree of anisocytosis (RBC size variation).
  • Calculated value using the MCV and RBC count.
  • Useful in early detection of iron deficiency anemia but should not replace other diagnostic tests.
  • RBC morphology.
  • WBC count, platelet count, and morphology. (Manual Differential).
  • Reticulocyte count.
  • Examination of bone marrow smears.
  • Malarial smears.
  • Osmotic fragility test - measures the ability of the red cells to take up fluids without lysing.
  • Sugar Water Screening Test.
  • Ham’s Acidified Serum Test.
  • Sickle cell testing and hemoglobin electrophoresis.
  • Pyruvate kinase - enzyme in the Embden-Meyerhof pathway.
  • Folic acid (folate) and vitamin B12 levels -- important in DNA synthesis.
  • Serum Iron levels.

PATHOPHYSIOLOGICAL CATEGORIES OF ANEMIA

Blood loss - acute or chronic.

Decreased or impaired red blood cell production.

  • Damage to or suppression of the bone marrow.
  • Deficiency of erythropoietic growth factors such as erythropoietin.
  • Abnormal metabolism of iron or insufficient iron storage causing problems in heme synthesis. Includes Vitamin and mineral deficiencies.
  • Defect in globin synthesis.

Accelerated destruction of the RBC.

  • Intrinsic defects within the RBC (hereditary).
    • Membrane defects or deficiencies.
    • Enzyme defects or deficiencies.
    • Hemoglobinopathies.
    • Defective globin synthesis.
    • Acquired paroxysmal nocturnal hemoglobinuria (PNH).
  • Extracorpuscular causes -- non-immune acquired hemolytic anemia.
    • Chemicals, toxins, venoms.
    • Physical trauma due to cardiac replacement valves, burns, disseminated intravascular coagulation (DIC).
    • Infectious agents such as malaria.
  • Extracorpuscular causes -- immune hemolytic anemia.
    • Isoimmune antibodies – Incompatible transfusion, hemolytic disease of the newborn (HDN).
    • Autoimmune antibodies – Warm reacting, cold reacting, and drug induced.
  • Miscellaneous. Liver disease, sulfhemoglobinemia.

Anemia classification schemes.

  • Wintrobe developed the first system based on morphology.
  • Other schemes categorize anemia by etiology (cause).
  • Others use major physiological or pathophysiological characteristics.

CLASSIFICATION OF ANEMIA’S BY MORPHOLOGY

Characterizes anemia based on the size of RBCs. Anemias are categorized as either macrocytic, normocytic, or microcytic. Major limitation is that it tells nothing of the etiology or reason for the anemia.

  • Macrocytic anemia (MCV > 100 fL).
  • Normocytic anemia (MCV 80-100 fL).
  • Microcytic anemia (MCV < 80 fL).

 

David L. Heiserman, Editor

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Revised: June 06, 2015