Complete Blood Count (CBC) in Practice
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Questions and Answers

What condition is most likely associated with a low RBC count due to impaired production?

  • Sickle cell anemia
  • Pernicious anemia (correct)
  • Hereditary spherocytosis
  • Polycythemia vera

    • Which factor is least likely to contribute to increased destruction of RBCs?

  • Autoimmune hemolytic anemia
  • Iron deficiency anemia (correct)
  • G6PD deficiency
  • Microangiopathic hemolytic anemia

    • How would you calculate the hematocrit if the RBC count is reported as 4.5 million/mm³?

  • Add 10 to the RBC count
  • Divide the RBC count by 3
  • Multiply the RBC count by 3 (correct)
  • Multiply the RBC count by 2.5

    • Which of the following conditions is directly linked to high RBC count (erythrocytosis)?

    <p>Thalassemia trait</p> Signup and view all the answers

    What normal value defines hematocrit for an adult female?

    <p>34-46.5%</p> Signup and view all the answers

    What does forward scatter mainly depend on in cell counting methods?

    <p>Cell size</p> Signup and view all the answers

    Which of the following is NOT a component of the three-part differential count?

    <p>Eosinophils</p> Signup and view all the answers

    What is a characteristic of automated blood cell counters with differential counting capacity?

    <p>They often provide a five- to seven-part differential count.</p> Signup and view all the answers

    In a five- to seven-part differential count, what additional cells may be included?

    <p>Immature granulocytes and atypical lymphocytes</p> Signup and view all the answers

    How do some three-part differential instruments categorize leukocytes?

    <p>Using a WBC-small cell ratio and WBC-large cell ratio</p> Signup and view all the answers

    What is a common limitation of instruments utilizing a three-part differential count?

    <p>They may misclassify a proportion of eosinophils as monocytes.</p> Signup and view all the answers

    Which characteristic of sideward scatter is primarily utilized in cell analysis?

    <p>Nuclear segmentation</p> Signup and view all the answers

    What is the importance of binding certain dyes in automated blood cell counting?

    <p>It assists in quantifying specific cell granules.</p> Signup and view all the answers

    Which condition could lead to a lower than normal hematocrit level?

    <p>Severe anemia</p> Signup and view all the answers

    What is the normal range of Hemoglobin (Hb) for adult females?

    <p>11.5-16.5 g/dl</p> Signup and view all the answers

    Which of the following best describes macrocytic anemia?

    <p>MCV &gt; 98 femtoliter</p> Signup and view all the answers

    What is the normal range for Mean Corpuscular Hemoglobin Concentration (MCHC)?

    <p>32-36 gm/dl</p> Signup and view all the answers

    What does a low Mean Corpuscular Volume (MCV) indicate?

    <p>Microcytic anemia</p> Signup and view all the answers

    Which of the following is true regarding Mean Cell Hemoglobin (MCH)?

    <p>Normal range of MCH is 27-31 picograms/cell</p> Signup and view all the answers

    Which factor is NOT typically associated with low hemoglobin (Hb) levels?

    <p>Polycythemia</p> Signup and view all the answers

    What physiological response occurs when the body senses low oxygen levels?

    <p>Production of more red blood cells</p> Signup and view all the answers

    Which factor primarily influences erythrocyte aggregation during the acute phase response?

    <p>Plasma protein composition</p> Signup and view all the answers

    How does the presence of hypoalbuminemia affect the erythrocyte sedimentation rate (ESR)?

    <p>It decreases the ESR values.</p> Signup and view all the answers

    In which type of anemia would patients likely show a higher ESR due to larger erythrocytes?

    <p>Macrocytic anemia</p> Signup and view all the answers

    What aspect of erythrocyte shape affects the ESR in conditions like sickle cell anemia?

    <p>Irregular shape and poor aggregation</p> Signup and view all the answers

    Which of the following diseases is associated with an elevated ESR?

    <p>Multiple myeloma</p> Signup and view all the answers

    What method is recommended by the CLSI for determining the erythrocyte sedimentation rate (ESR)?

    <p>Westergren method</p> Signup and view all the answers

    What is the role of acute-phase proteins like fibrinogen in the ESR?

    <p>They facilitate erythrocyte aggregation.</p> Signup and view all the answers

    What measurement is taken at the end of the Westergren method for ESR?

    <p>The height of the sedimented erythrocyte column</p> Signup and view all the answers

    What is the primary cause of thrombocytopenia linked to peripheral consumption and destruction?

    <p>Splenomegaly</p> Signup and view all the answers

    Which condition is primarily associated with an increased mean platelet volume (MPV)?

    <p>Immune thrombocytopenic purpura (ITP)</p> Signup and view all the answers

    What is the normal range for plateletcrit (PCT) expressed as a percentage?

    <p>0.22–0.24%</p> Signup and view all the answers

    What could cause a spurious higher platelet count in a blood sample?

    <p>EDTA induced platelet clumping</p> Signup and view all the answers

    Which condition is indicated by thrombocytopenia with low mean platelet volume (MPV)?

    <p>Wiskott Aldrich syndrome</p> Signup and view all the answers

    What does an increased platelet volume distribution width (PDW) indicate?

    <p>Platelet anisocytosis</p> Signup and view all the answers

    Which of the following is NOT a marker of platelet activation?

    <p>Plateletcrit (PCT)</p> Signup and view all the answers

    What is the normal range for platelet larger cell ratio (P-LCR)?

    <p>15–35%</p> Signup and view all the answers

    What is the significance of enumerating nucleated red blood cells (NRBC) in blood counts?

    <p>Their presence can directly affect the accuracy of the white blood cell count.</p> Signup and view all the answers

    What method is primarily used by instruments to determine the presence of NRBC?

    <p>Staining with a nuclear dye and analyzing light scatter or flow cytometry.</p> Signup and view all the answers

    How are nucleated red blood cells (NRBCs) reported in blood analysis?

    <p>As the number of NRBCs per 100 white blood cells.</p> Signup and view all the answers

    What happens during the first phase of the Erythrocyte Sedimentation Rate (ESR)?

    <p>Erythrocytes form aggregations known as rouleaux.</p> Signup and view all the answers

    When an automated blood counter flags a sample, what does it indicate?

    <p>There may be a significant abnormality requiring further examination.</p> Signup and view all the answers

    What is the primary method used for hemoglobin measurement in some automated counters?

    <p>Modification of the manual HiCN method with cyanide reagents.</p> Signup and view all the answers

    What is the consequence of the nuclear size of an NRBC being below the instrument's white blood cell threshold?

    <p>They are excluded from the automated white blood cell count entirely.</p> Signup and view all the answers

    Which phase in ESR is characterized by erythrocytes forming aggregates and settling out of solution?

    <p>Phase 2 - Sedimentation Phase.</p> Signup and view all the answers

    Study Notes

    Complete Blood Count (CBC) in Practice

    • CBC is the most common test in clinical medicine.
    • It helps determine the type and severity of blood cell abnormalities.
    • Modern CBCs are fully automated and highly reproducible.
    • Correct CBC interpretation reduces unnecessary blood smears.
    • Provides useful information for provisional diagnosis of RBC and WBC diseases.

    Components of Automated CBC

    • Blood count basic parameters: Hb, Hct, RBC, WBC, platelets.
    • Red cell indices: MCV, MCH, MCHC, RDW
    • WBC differentials
    • Platelets count and indices
    • Reticulocyte count

    Advantages of Automation

    • Increased efficiency and streamlined workflow
    • Increased productivity
    • Increased test volumes without additional staff
    • Reduced turnaround time (TAT) and improved service
    • Decreased costs

    Basic Principles of Automated Blood Cell Analyzers

    • Electrical Impedance:
      • Red cells are poor conductors of electricity, while diluents are good conductors.
      • This difference forms the basis of cell counting systems (Coulter Principle).
      • Whole blood passes through a narrow aperture between electrodes.
      • Impedance change is proportional to cell volume, enabling cell counts and volume measurements.
      • Analysis provides CBCs and three-part WBC differentials(granulocytes, lymphocytes, and monocytes).
      • Cannot distinguish between similarly sized granular leukocytes (eosinophils, basophils, and neutrophils).
      • Counting rates of up to 10,000 cells per second are possible.
      • Typical analysis takes less than a minute.
    • Light Scattering:
      • Microscopic particles, like blood cells, scatter incident light into small angles (0-15°).
      • Correlating different optical signals enables cell classification in a multi-dimensional space.
      • Forward scatter (low-angle) depends on cell size.
      • Side scatter (90 degrees) reflects nuclear segmentation and cytoplasmic granule number.

    Automated Differential Count

    • Most modern counters use flow cytometry integrated into a full blood counter.
    • Increasingly, automated counters offer three- or five- to seven-part differential counts.
    • Counting is performed on diluted whole blood where red cells are either lysed or rendered transparent.
    • Analysis might depend on cell volume, physical characteristics, or binding of dyes to granules or cellular enzyme activity (e.g., peroxidase).

    Three-Part Differential

    • Classifies cells into granulocytes (large cells), lymphocytes (small cells), and monocytes (middle cells).
    • In practice, some eosinophils and basophils are often counted in the monocyte category.

    Five and Seven-Part Differentials

    • Classifies cells as neutrophils, eosinophils, basophils, lymphocytes, and monocytes.
    • Extended counts may include immature granulocytes or large immature cells (blasts) and atypical lymphocytes.
    • Automated instruments can flag samples with elevated counts of specific cell types (like NRBCs, myelocytes, promyelocytes, blasts, or atypical lymphocytes).

    Automated Nucleated Red Blood Cell (NRBC) Count

    • NRBC enumeration is crucial for accurate WBC determination in some automated counters.
    • NRBCs are reported as a number per 100 white blood cells.
    • Subtracting NRBC count from the total nucleated count provides the correct WBC count.
    • Instruments might misclassify NRBCs with low nuclear size thresholds.
    • Using nuclear dyes and flow cytometry or fluorescence laser light scatter techniques separate NRBCs from WBCs.

    Flagging of Automated Blood Counts

    • Flags signal potential significant abnormalities in analyzed blood samples.
    • Operators need confirmation through microscopic examination.
    • Hematology analyzers flag abnormal cells for review.

    Measurement of Hemoglobin (Hb)

    • Some automated counters measure Hb by modifying the manual HiCN method, using cyanide reagents.
    • Diluting blood in potassium cyanide and potassium ferricyanide solution converts hemoglobin to HiCN.
    • Solution absorbance is measured at 540 nm using a spectrometer or photoelectric colorimeter with a yellow-green filter.

    Erythrocyte Sedimentation Rate (ESR)

    • Measures the rate at which erythrocytes settle from plasma.
    • Process involves aggregation (rouleaux formation), sedimentation, and packing phases.
    • ESR depends on plasma protein composition, erythrocyte size/shape and concentration.
    • Positive plasma proteins neutralize erythrocyte surface charge, decreasing repulsion and promoting aggregation.
    • Increased ESR may indicate inflammatory conditions, chronic diseases, and some hematological abnormalities.
    • Reduced ESR is associated with conditions like hypoalbuminemia and certain anemias.

    CBC Automation and Interpretation: RBC Indices

    • RBC Count: Measures the actual number of red blood cells per blood sample.
    • Normal ranges vary by sex.
    • Low RBC count usually indicates anemia (e.g., blood loss; impaired production; increased destruction).
    • High RBC count can be due to various factors, including polycythemia vera, smoking, and high altitude.
    • Hematocrit (HCT): Ratio of red blood cell volume to total blood volume, expressed as a percentage.
    • Correlates with RBC count (high/low HCT = high/low RBC count).
    • Hemoglobin (Hb): Oxygen-carrying protein in red blood cells.
    • Normal values depend on age and sex.
    • Low Hb indicates anemia; high Hb suggests polycythemia.
    • MCV: Average volume of red blood cells.
      • <78 fL = microcytic anemia
      • 78-98 fL = normocytic anemia

      • 98 fL = macrocytic anemia

    • MCH: Average mass of hemoglobin per red blood cell.
    • MCHC: Hemoglobin concentration per unit volume of packed red blood cells.
      • <32 g/dL = hypochromic anemia

      • 36 g/dL = hyperchromic anemia

    • RDW: Variation in red blood cell volume. High RDW usually indicates mixed or multiple causes of anemia.

    White Blood Cell (WBC) Differential

    • Normal ranges of WBC counts vary by age.
    • Low WBC count (leukopenia) suggests various causes including infection, inflammation, drug administration, malignancy, aplastic anemia and severe nutritional deficiencies.
    • High WBC count (leukocytosis) can result from infection, inflammation, drug administration, malignancy, myeloproliferative disorders, and leukemoid reaction.
    • Different WBC types include granulocytes (neutrophils, eosinophils, basophils), and agranulocytes (lymphocytes, monocytes).

    Platelet Count and Indices

    • Normal platelet counts vary.
    • Elevated platelet count (thrombocytosis) may be reactive to various conditions (blood loss, infection, inflammation).
    • Reduced platelet count (thrombocytopenia) arises from peripheral consumption, production failure, or other factors.
    • Instruments may miscount platelets where there are RBC microcytosis/fragmentation.
    • Platelet indices include plateletcrit (PCT), mean platelet volume (MPV), platelet distribution width (PDW), and platelet larger cell ratio (P-LCR).

    Histograms

    • CBC histogram analysis offers early stage differential diagnoses in disease processes.
    • WBC histograms depict lymphocyte, mixed cell population and neutrophil distribution.
    • RBC and platelet histograms use arbitrary lines for platelet and RBC separation.

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    Interpretation of CBC in Practice PDF

    Description

    This quiz covers the essentials of Complete Blood Count (CBC) tests, focusing on their significance in clinical medicine. It discusses the components of automated CBC, the advantages of automation, and the basic principles of blood cell analyzers. Test your knowledge on how CBC aids in diagnosing blood cell abnormalities and improving laboratory efficiency.

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