Blood smear (Peripheral blood smear, Red blood cell [RBC] morphology, RBC smear)
المؤلف:
Kathleen Deska Pagana, Timothy J. Pagana, Theresa Noel Pagana.
المصدر:
Mosbys diagnostic and laboratory test reference
الجزء والصفحة:
15th edition , p151-153
2025-10-28
71
Type of test Blood
Normal findings
Normal quantity of red and white blood cells (RBCs, WBCs) and platelets
Normal size, shape, and color of RBCs
Normal WBC differential count
Normal size and granulation of platelets
Test explanation and related physiology
Examination of the peripheral blood smear can provide a significant amount of information concerning drugs and diseases that affect erythrocytes (RBCs), leukocytes (WBCs), or platelets. Furthermore, other congenital and acquired diseases can be diagnosed. When special stains are applied to the blood smear, leukemia, infection, infestation, and other diseases can be identified.
When adequately prepared and examined microscopically by an experienced technologist or pathologist, a smear of peripheral blood can be very diagnostic. All three hematologic cell lines— RBCs, platelets, and WBCs—can be examined. In the peripheral blood, five different types of WBCs can routinely be identified: neutrophils, eosinophils, basophils, lymphocytes, and monocytes. The first three are also referred to as granulocytes. Please see the discussion in bone marrow biopsy for more information concerning the various elements of blood.
Microscopic examination of the RBCs can reveal variations in RBC size (anisocytosis), shape (poikilocytosis), color, or intracellular content (Box 1). Classification of RBCs according to these variables is most helpful in identifying the causes of anemia and the presence of other diseases.
Box1. Microscopic examination of red blood cells
The WBCs are examined for total quantity, differential count, and degree of maturity. An increased number of immature WBCs may indicate leukemia or infection. A decreased WBC count indicates a failure of marrow to produce WBCs (because of drugs, chronic disease, neoplasia, or fibrosis), peripheral destruction, or sequestration.
Platelet examination
Finally, an experienced laboratory technologist also can estimate platelet number. Platelets are small cell fragments that do not contain a nucleus. The contents of the granules in a platelet are released to promote clotting.
Procedure and patient care
Before
* Explain the procedure to the patient.
* Tell the patient that no fasting is required.
During
• Collect a drop of blood from a finger stick or heel stick and place it on a slide.
• If necessary, perform a venipuncture and collect the blood in a lavender-top tube.
• Note that a blood smear is first studied with an automated cytometer programmed to recognize abnormal blood cell shapes and other variations. An evaluation smear is performed by a technologist. Low counts may be hand counted to ensure accuracy. The most accurate smear requires review by a pathologist.
After
• Apply pressure to the venipuncture site.
Abnormal findings
See Box 1 in the Test explanation and related physiology section.
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