Red Blood Cell Smear (Morphology)

When adequately prepared and examined microscopically by an experienced technologist and pathologist, a Smear of Peripheral Blood is the most informative of all hematologic tests. All three hematologic cell lines—erythrocytes (Red Blood Cells), platelets, and leukocytes (White Blood Cells)—can be examined. In the peripheral blood, five different types of leukocytes can routinely be identified—neutrophils, eosinophils, basophils, lymphocytes, and monocytes. The first three are also referred to as Granulocytes.


Microscopic examination of the Red Blood Cells can reveal variations in RBC size (anisocytosis), shape (poikilocytosis), color, or intracellular content. Classification of RBCs according to these variables is most helpful in identifying the causes of anemia and the presence of other diseases. The following are the possible causes of abnormality that can seen microscopically on Red Blood Cells:




Causes of Red Blood Cell Size Abnormalities

Causes of Abnormally Small Red Blood Cells (Microcytes)

  • Iron deficiency.
  • Thalassemia.
  • Hemoglobinopathies.


Causes of Abnormally Large Red Blood Cells (Macrocytes)

  • Vitamin B12 or folic acid deficiency.
  • Reticulocytosis is secondary cause to increased erythropoiesis (RBC production).
  • Occasional Liver Disorder.




Causes of Red Blood Cell Shape Abnormalities

Causes of Abnormally Small and Round  RBCs (Spherocytes)

  • Hereditary Spherocytosis.
  • Acquired Immunohemolytic Anemia.


Causes of Crescent Shaped Red Blood Cells (Elliptocytes)

  • Hereditary Elliptocytosis.


Causes of Thin RBCs with less Hemoglobin (Codocytes)

  • Hemoglobinopathies.
  • Thalassemia.


Causes of Burr Red Blood Cells (Echinocytes)

  • Uremia
  • Liver Disease




Causes of Red Blood Cell Color Abnormalities

Causes of Pale Red Blood Cells (Hypochromic)

Pale Red Blood Cells is an indication of Low Hemoglobin Levels. Causes of Pale RBCs are:

  • Iron deficiency.
  • Thalassemi.


Causes of Dark Red Blood Cells (Hyperchromasia)

Dark or more colored Red Blood Cells indicate that the cell has a high Hemoglobin concentration which is usually caused by dehydration, living at high altitude, or other causes of High Hemoglobin Levels.




Causes of Red Blood Cell Intracellular Structure

Causes of Nucleated Red Blood Cells (normoblasts)

Red Blood Cells normally do not have a nucleus. Immature Red Blood Cells however do have a nucleus. Immature nucleated RBCs indicate increased RBC synthesis which is caused by:

  • Anemia.
  • Chronic Hypoxemia.
  • Marrow-occupying neoplasm or fibrotic tissue.


Causes of Red Blood Cells Basophilic Stapling

Red Blood Cells Basophilic Stapling refers to bodies enclosed or included in the cytoplasm of the RBCs. Seeing such bodies can be caused by:

  • Lead poisoning.
  • Reticulocytosis.


Causes of Red Blood Cells with Howell-Jolly Bodies

Howell-Jolly bodies are small round remnants of nuclear material remaining within the RBC. These usually caused by:

  • Surgical Splenectomy (Partial or complete removal of spleen).
  • Hemolytic Anemia.
  • Megaloblastic Anemia.
  • Functional Asplenia which occurs after splenic infarction.