Blood Smear: Details on RBCs, WBCs

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Also known as: Peripheral Smear; Blood Film; Manual Differential; Differential Slide; Red Blood Cell Morphology; Erythrocyte Morphology; Leukocyte Differential
Formal name: Peripheral Blood Smear

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Details: Red Blood Cell Irregularities

SIZE

SHAPE -- Poikilocytosis is a variation in the shape of an RBC and may include several different abnormalities at the same time.

  • Acanthrocytes (spur, thorn or spiculated cells): irregular shaped cells with 5-10 spicules; may be present in the blood of people who have had their spleen removed (splenectomy) and with, for example, chronic alcoholism (cirrhosis), hemolytic anemia, thalassemia, or severe burns. They are present in an inherited disorder called abetalipoproteineimia.
  • Echinocytes (burr, crenated or berry cells): may have 10-30 spiny projections and often seen in people with renal failure or iron deficiency; may be an artifact – something caused during sample preparation.
  • Elliptocytes (ovalocyte): elliptical-shaped RBC seen in hereditary elliptocytosis and various anemias.
  • Keratocyte (horn cell):  a half-moon or spindle-shaped RBC that may be seen in people with disseminated intravascular coagulation (DIC) or a vascular artificial device (prosthesis) such as a heart valve.
  • Rouleaux: RBCs that appear as a stack of coins and seen in people with multiple myeloma or Waldenstrom macroglobulinemia.
  • Sickle cells: crescent-shaped RBCs that are characteristic of sickle cell anemia.
  • Target cells (leptocytes or codocytes): RBCs that resemble a bull's-eye; commonly seen in people with abnormal inherited forms of hemoglobin (hemoglobinopathies), thalassemia, and various anemias.
  • Teardrop cells (dacrocytes): RBCs that resemble a teardrop; often seen in people with myelofibrosis and thalassemia.
  • Schistocytes: fragments or broken pieces of RBCs; this may be due to a disorder that is causing the red blood cells to be especially fragile or due to mechanical damage as seen sometimes with devices such as artificial heart valves, or in severely burned patients.
  • Spherocytosis: sphere-shaped RBCs that are often present in hereditary spherocytosis or due to an immune hemolytic anemia.
  • Spicule (crenated): scalloped or serrated perimeter due to loss of water from the cell or to liver disease.

COLOR

  • Hypochromasia: this may be seen in a variety of disorders including thalassemia and iron deficiency. The RBC is pale in color due to insufficient hemoglobin and contains a large, hollow middle (central pallor) of the cell.
  • Hyperchromasia: the RBC is darker in color that normal; this may be due to dehydration.
  • Polychromasia: blue-staining RBCs, indicating that they are immature due to early release from the bone marrow.

Intracellular Structure (nuclear material, remnants, and inclusions inside the RBC)

  • Nucleated RBCs (NRBC, normoblasts): a very immature form of RBCs seen when there is a severe demand for RBCs to be released by the bone marrow. May be seen in severe anemia, myelofibrosis, thalassemia, miliary tuberculosis, cancers that involve the bone marrow, and in chronic low oxygen levels (hypoxemia). Nucleated RBCs can be normal in infants for a short time after birth.
  • Reticulocytes: these are immature RBCs that are usually a blue-staining (polychromatic) color. A few of these young red blood cells are normal in the circulation. Elevated numbers may be seen with acute blood loss, hypoxia, RBC destruction, sickle cell disease, glucose-6-phosphate dehydrogenase (G6PD) deficiency, and autoimmune hemolytic anemia.
  • Siderocyte, sideroblast, ringed sideroblast: When RBCs are stained with Prussian blue dye, iron granules may be seen. Sideroblasts are immature siderocytes and may actually form a ring pattern indicative of sideroblastic anemia.
  • Basophilic stippling is dark blue dots inside the RBC; due to the precipitation of nuclear material (ribosomes) and may be present in heavy metal poisoning (such as lead), nutritional deficiencies, or myelofibrosis.
  • Heinz bodies: large inclusion bodies (granules) in the RBCs when stained with crystal violet; may be due to an enzyme (G6PD) deficiency, unstable hemoglobin variant, thalassemia, and autoimmune hemolytic anemia.
  • Howell-Jolly bodies (small, round remnants of nuclear DNA inside cell): present in sickle cell anemia, hemolytic or megaloblastic anemias, and may be seen after a splenectomy.
  • Cabot's Rings: threadlike inclusions that form a ring within the RBC; may be seen in a variety of anemias.
  • Malarial parasites: in people with malaria, these parasites live inside RBCs and may be visible on a blood smear. This is not a routine finding; these parasites are usually found in those who live in or have traveled to areas where the disease is endemic.

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