RBC-Lab

Overview of Abnormal Red Blood Cell Morphologies

  • Keratocyte (Blister Cell)

    • Definition: Red blood cell with a small blister on the edge.
    • Description: If the blister breaks, it produces two projections resembling "Dracula's teeth"; if one tooth falls out, the cell is likened to a "toothless Dracula".

  • Schistocyte

    • Definition: Fragmented red blood cell indicative of shearing.
    • Characteristics: Smaller volume compared to normal red blood cells.

  • Spherocyte

    • Definition: Spherical red blood cell that has lost its biconcave shape.
    • Clinical Significance: Indicative of immune-mediated hemolytic anemia (IMHA).
    • Important Note: Identification only reliable in dogs due to central power; less recognition in cats and horses.

  • Heinz Body

    • Definition: An aggregate of oxidatively damaged hemoglobin forming a ball on the red blood cell, producing a "nose" effect.
    • Appearance: May be visible as a pale circle when viewed from the side.

  • Eccentric Site

    • Definition: Oxidatively indented red blood cell with part of the membrane fused; hemoglobin displaced to one side.
    • Description: One side appears diffusely red while the other appears pale.

  • Macrocyte

    • Definition: A larger than normal red blood cell.

  • Microcyte

    • Definition: A smaller than normal red blood cell.

  • Polychromasia (Polychromatophil)

    • Definition: Red blood cell with a blue cast, indicating it is a younger cell.

  • Howell-Jolly Body

    • Definition: Nuclear remnant found within red blood cell; resembles a deep, basophilic mark on the cell.

  • Basophilic Stippling

    • Definition: Multiple pinpoint blue dots dispersed throughout the red blood cell's cytoplasm, resembling chickenpox.

  • Target Cell

    • Definition: Red blood cell that appears as a target with darker and lighter areas in concentric circles.
    • Description: When viewed from the side, it resembles three bubble layers stuck together.

Clinical Implications of Morphologies

  • Acanthocytes, Keratocytes, Schistocytes:

    • All occur with fragmentation; schistocytes are the most specific for this condition.
    • Acanthocytosis may occur with liver disease or lipid disorders.
    • Keratocytes may result from oxidative injury to the red blood cells.

  • Spherocytes:

    • Primarily indicative of IMHA; other rare causes exist but focused on IMHA for this context.

  • Heinz Bodies & Eccentric Sites:

    • Both morphologies suggest oxidative injury to red blood cells.

  • Polychromasia, Howell-Jolly Bodies, Basophilic Stippling, Target Cells:

    • Indicate red cell regeneration; polychromasia is the only specificity for it.
    • Howell-Jolly bodies can relate to bone marrow disease or splenic dysfunction.
    • Basophilic stippling may indicate lead toxicity.
    • Target cells may indicate iron deficiency, liver disease, or lipid disorders.

Centrifuge Process for Blood Samples

  • Blood Sample Preparation:

    • Blood collected in a lavender top tube (anticoagulated).
    • Use pneumatic tubes (without additives) for transferring samples.
    • Ensure samples are well mixed in the container before filling tubes 2/3 full for centrifugation.

  • Centrifuge Procedure:

    • Place the tubes in a hematocrit centrifuge, ensuring equilibrated balance.
    • Spin for three minutes; upon completion, remove tubes to observe the distinct layering of plasma and red blood cells.

  • Calculating Packed Cell Volume (PCV):

    • Use a hematocrit reader card; align blood line bottom with the zero line and top of plasma with the top line.
    • Patient's PCV measured at 51%, considered high-normal (normal range: 35-50%).

  • Total Solids Measurement:

    • Conducted simultaneously with PCV; requires the refractometer for reading plasma protein concentration.
    • Break the tube above the red cell-plasma interface, ensuring no glass shards in the sample.
    • In this instance, the total solids recorded at 8.0 grams per deciliter indicates circulating plasma protein levels.

Blood Smear Preparation

  • Equipment Required:

    • Well mixed, unclotted EDTA tube for sample.
    • Use beveled slides for smear preparation, avoiding poor-quality slides which impede smear-making.

  • Steps for Blood Smear Preparation:

    • Ensure sufficient blood volume for adequate drop size; a medium-sized drop is ideal.
    • Hold spreader at approximately 45 degrees, anchoring with fingers for stability.
    • Push the spreader across the blood drop swiftly to create a thin smear shape.

  • Common Mistakes to Avoid:

    • Avoid the "Olympic ski jump" technique; maintain pressure and control during smear creation.
    • Do not rush or admire your work mid-process to prevent thickness or unevenness in the smear.

  • Staining Process:

    • Dip stained slides in the correct sequence of solutions, in an appropriate order from lightest to darkest; five dips for one second each and a clean water rinse.
    • Air dry final slides and avoid mounting unless absolutely necessary, as oil application is preferred for focusing before examination.

Summary of Blood Analysis Calculations

  • Red blood cell estimate (RBC):

    • Formula:
      RBC=PCV6\text{RBC} = \frac{\text{PCV}}{6}
      Example: For \text{PCV} = 45, \text{RBC} \approx 7,500,000

  • Hemoglobin estimate (Hb):

    • Formula:
      Hb=PCV3\text{Hb} = \frac{\text{PCV}}{3}
      Example: For \text{PCV} = 45, \text{Hb} = 15

  • Mean Corpuscular Volume (MCV):

    • Formula:
      MCV=PCVRBC×10\text{MCV} = \frac{\text{PCV}}{\text{RBC}} \times 10
      Example: For \text{PCV} = 45 and \text{RBC} \approx 7,500,000, \text{MCV} = 60 \text{mL}

  • Mean Corpuscular Hemoglobin (MCH):

    • Formula:
      MCH=Hb×10RBC\text{MCH} = \frac{\text{Hb} \times 10}{\text{RBC}}
      Example: For \text{Hb} = 15 and \text{RBC} \approx 7,500,000, \text{MCH} \approx 3.3

  • Final Note: When documenting blood smear results, ensure to include patient information for clarity and accuracy.