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What are the steps in the performance of a peripheral blood smear examination?
Determine the overall staining quality, check distribution of cells, find an optimal area for examination, perform a WBC estimate, and evaluate RBC morphology.
Which term refers to a variation in red cell size?
Normal red blood cells are larger than the nucleus of a small lymphocyte.
False
Define hypochromic red cells.
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What is the primary function of red blood cells?
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What is the lifespan of a mature red blood cell?
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The average diameter of a normal red blood cell is around _____ µm.
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Which condition is characterized by 'stacked coin' formation of red blood cells?
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What does the erythrocyte sedimentation rate (ESR) measure?
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ESR can indicate one specific disorder or disease.
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Match the following terms with their definitions:
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What is C-reactive protein (CRP)?
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Which of the following conditions is NOT associated with high levels of CRP?
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CRP testing is faster but often more expensive than ESR testing.
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What does a high-sensitivity CRP (hsCRP) test specifically indicate?
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Which of the following conditions is associated with abnormal clinical conditions that show increased serum viscosity?
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What term describes a significant variation in red blood cell size?
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A normal MCV is considered to be between 80 to 100 fL.
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What characterizes macrocytes?
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What is the typical appearance of spherocytes in blood smears?
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Match the following terms with their definitions:
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The average size of the erythrocyte is indicated by the measurement of the __________.
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Study Notes
Peripheral Blood Smear Examination
- A blood smear examination may be performed for a variety of reasons, including physician request, an abnormality discovered in a previous CBC, or a flagged result from the hematology analyzer
- A flagged result indicates an abnormal finding that requires further investigation
- All laboratories should have established documentation of the procedures and guidelines for smear review
- A careful and thorough examination via light microscopy provides valuable information about cell morphology
- The examination should include evaluation of RBC, WBC, and PLT morphology
- The technologist should review at least 10 high-power (100X) oil immersion fields (OIF)
Steps in Peripheral Blood Smear Examination
- Low-power (10×) Scan: Determine the overall staining quality of the blood smear, the distribution of cells, and find an optimal area for detailed examination.
- High-Power (40×) Scan: Perform a WBC estimate in at least 10 fields, averaging the number of WBCs/hpf (2-6 WBCs/hpf is considered normal).
- Oil Immersion (100×) Examination: Perform a 100 WBC differential count and evaluate the RBCs for size, shape, color, and inclusion abnormalities. Perform a platelet estimate and evaluate platelet morphology.
- Platelet Estimate: Count the number of platelets in 10 OIFs, calculate the average, and multiply by 15 if using an automatic slide maker, or 20 for manual preparations.
Normal RBC Morphology
- Normal RBCs on a Wright stained smear are reddish-pink, have a diameter of ~ 6 - 8 µm, with a ~ 5% variation in size
- Normal RBCs have an average volume of 90 fL (MCV), and a central pallor that is approximately 1/3 the size of the cell.
- The main function of an RBC is to produce hemoglobin to carry oxygen to tissues and organs
- Mature RBCs lack a nucleus and organelles
- RBCs have a life-span of ~ 120 days
Red Blood Cell Abnormalities
- When examining a blood smear for abnormalities, consider the following:
- Is the abnormality seen in every field?
- Is the morphology pathological, or artificially induced?
- Key factors to consider when assessing red cell abnormalities include:
- Size Variation (Anisocytosis)
- Shape Variation (Poikilocytosis)
- Color Variation (Degree of Hemoglobinization)
Anisocytosis
- Anisocytosis indicates a significant variation in red blood cell size
- It is often found in leukemias and various forms of anemia
- Grading: 1+, 2+, 3+, 4+
Variations in Red Blood Cell Distribution
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Normal Distribution: Cells are slightly separated from each other without overlap in the thin portion (body) of the smear
-
Abnormal Distribution: May include:
- Rouleaux Formation: Red blood cells appear like stacks of coins, often due to increased plasma proteins, potentially due to delay in spreading the blood, or a too-thick smear.
- Autoagglutination: Clumps of red blood cells formed due to an antigen-antibody reaction, may be seen in cold antibody syndromes like Paroxysmal Cold Hemoglobinuria
Agglutination
- Agglutination is an aggregation of red cells forming random clusters
- It is a result of an antigen-antibody reaction within the body
- It is often associated with cold antibody syndromes, like Cold Agglutination Disease (CAD) and Paroxysmal Cold Hemoglobinuria (PCH)
- Warming the sample to 37°C may help break up agglutinins, allowing for normal slide preparation
Rouleaux Formation
- Red cells appear stacked on one another, often due to high levels of globulins or fibrinogen in the plasma
- Associated with conditions like multiple myeloma (MM) and Waldenstrom’s Macroglobulinemia (WM)
- May also be present in chronic inflammatory disorders and lymphomas
Variations in RBC Size (Anisocytosis)
- Microcytic: MCV < 80 fL.
- Normocytic: MCV = 80 - 100 fL.
- Macrocytic: MCV > 100 fL
Erythrocyte Sedimentation Rate (ESR)
- The ESR measures the settling of red blood cells in diluted plasma over a specific period
- It is reported in mm/hour
- The ESR test is non-specific and does not indicate a definitive disorder or disease
- Factors affecting ESR include age, gender, and the presence of rouleaux/agglutination, increased immunoglobulins, and anisocytosis
C-Reactive Protein (CRP)
- A protein produced in the liver
- High levels indicate inflammation
- Considered a semi-specific marker for inflammatory conditions such as systemic lupus erythematosus (Lupus), coronary artery disease, liver disease, inflammatory bowel disease (IBD), Chrohn’s Disease, and bacterial/viral infections
- CRP tests are faster than ESR tests, but often more expensive
- High sensitivity CRP (hsCRP) is considered a specific marker for heart disease and stroke
Serum Viscosity Test
- Specific test for hyperviscosity and hyperglobulinemia
- Normal serum viscosity compared to water is 1.5
- Abnormal conditions with increased serum viscosity include: o Waldenstrom's macroglobulinemia (increased IgM proteins) o Multiple myeloma (increased IgG proteins) o Polycythemia (increased RBCs)
- Rouleaux and/or agglutination on a peripheral blood smear may indicate hyperviscosity
Anisocytosis
- Abnormal cell development, potentially due to iron, vitamin B12, or folic acid deficiency, or a congenital defect.
- Cell size deviation from the norm of 7µm is referred to as microcyte (≤6 µm) or macrocyte (≥9 µm).
- Anisocytosis is graded 1+ to 4+ depending on the extent of size variation.
Normocytes
- Normal red blood cell size, with a mean corpuscular volume (MCV) of 80 to 100 fL.
- No significant size variation observed in the blood smear.
- A di-morphic population (mixture of large and small cells) can be caused by recent blood transfusion or recovery from anemia.
Macrocytes
- Red blood cells with MCV greater than 100 fL.
- Often associated with impaired DNA synthesis, resulting in megaloblastic erythropoiesis (large cell size) and macrocytic anemia.
- Common causes include vitamin B12 or folate deficiency, chemotherapy, or any nuclear maturation defect.
Non-megaloblastic Macrocytosis
- Caused by accelerated erythropoiesis, often due to acute blood loss or alcoholism.
- Cells are released prematurely from the marrow, appearing larger than mature erythrocytes.
- Neutrophilic hypersegmentation is typically not observed.
- Other potential causes: hypothyroidism, bone marrow disorders, neonatal blood, post-splenectomy, and excess plasma cholesterol.
Microcytes
- Red blood cells with MCV less than 80 fL.
- Hemoglobin content can be normal or decreased, leading to microcytic anemia.
- Impaired hemoglobin synthesis contributes to microcytic, hypochromic (low MCHC) cells.
Spherocytes
- Characterized by a reduced surface-to-volume ratio, resulting in a dense, round cell with no central pallor.
- Primarily caused by abnormalities of the red cell membrane, either hereditary or acquired.
- Commonly seen in hereditary spherocytosis (HS), a genetic disorder affecting membrane proteins such as spectrin, ankyrin, band 3, and protein 4.2.
- Also observed in autoimmune hemolytic anemia (AIHA), where antibodies coat the red cells, leading to membrane loss and spherocyte formation.
Target Cells (Codocytes)
- Appear as “targets” on blood smears due to excess membrane cholesterol and phospholipids.
- The true circulating form is bell-shaped.
- Most commonly seen in hemoglobinopathies, thalassemias, and liver disease.
Stomatocytes
- Have a central pallor resembling a mouth-like slit.
- Associated with membrane defects and abnormalities in red cell cation permeability.
- Can be acquired or congenital.
- Increased permeability to sodium, resulting in increased osmotic fragility.
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Description
This quiz explores the important aspects of performing a peripheral blood smear examination. It covers the procedures, guidelines, and the necessary evaluations to ensure accurate results, including assessment of RBC, WBC, and PLT morphology. Test your knowledge on light microscopy techniques and the steps involved in smear examination.
