Hematological Examinations and Diagnoses

Special Hematological Examinations

  • Special hematological examinations play a crucial role in diagnosing a variety of blood disorders.

Bone Marrow Examination

  • The bone marrow examination includes:
    • Clinical judgment by physicians.
    • Sample handling and smear preparation.
  • Many conditions can be assessed through bone marrow examination, including:
    • Hematologic and non-hematologic neoplasia.
    • Cytopenias.
    • Metabolic infections.

Bone Marrow Aspirations and Biopsies

  • Common Sites for Bone Marrow Sampling:
    • Posterior superior iliac crest
    • Anterior superior iliac crest
    • Sternum
    • Tibia (anterior medial surface)
  • The posterior superior iliac crest is favored for its accessibility and relative safety.

Bone Marrow Specimen Types

  • Bone marrow specimens typically consist of:
    • Aspirate: Provides information on morphologic variance of hematologic cells.
    • Core biopsy: Demonstrates bone marrow architecture, spatial relationships of hematological cells to fat, connective tissue, and bony stroma.
    • Used to estimate cellularity, with core biopsies being crucial in assessing overall marrow structure.

Fixatives for Bone Marrow Specimens

  • Various fixatives are utilized to prepare bone marrow specimens for analysis including:
    • Zenker fixative (potassium dichromate)
    • B5 fixative (mercuric chloride, sodium sulfate, glacial acetic acid)
    • 10% neutral formalin (preserves cell morphology)

Dry Tap and Specimen Collection Issues

  • Dry Tap: Occurs in cases of:
    • Fibrosis
    • Aplastic anemias
    • Packed with leukemic cells.
  • Complications such as dry tap limit the amount and types of analysis that can be performed.

Advantages and Disadvantages of Bone Marrow Techniques

  • Aspirate Smear:
    • Advantages: Fast, quantifies cell types, minimal processing needed.
    • Disadvantages: May not represent all cells due to dry taps, doesn’t show architecture.
  • Core Biopsy:
    • Advantages: Allows for analysis of both cells and stroma.
    • Disadvantages: Time-consuming process, requires decalcification.

Preparation of Bone Marrow Specimens

  • Direct Aspirate Smears:
    • Prepared from aspirated bone marrow drops on microscope slides, may be stained or unstained.
  • Crush Smears: Alternative approach using anticoagulated aspirate.
  • Buffy Coat Smears: Involves centrifugation and isolation of nucleated cells for analysis.

Staining Techniques

  • Common stains used in bone marrow examination:
    • Wright or Wright-Giemsa stains: Standard for blood cell morphology.
    • Prussian Blue: Used for detecting iron stores.
    • Cytochemical Stains: Important for identifying maturation stages of bone marrow cells (e.g., Myeloperoxidase, Sudan Black B).

Hematological Tests for Diagnosis of Anemia

  • Serum Iron: Normal range is 50 to 160 μg/dL, lower in iron deficiency.
  • Total Iron Binding Capacity (TIBC): Measures iron transport capability, increased in iron deficiency anemia (IDA).
  • Ferritin Levels: Reflect iron storage; important for diagnosing IDA and other deficiencies.
  • Erythrocyte Survival Studies: Assess longevity and breakdown of RBCs, often using radioactive chromium.
  • Osmotic Fragility Test: Evaluates red blood cell stability in varying saline concentrations to identify conditions like hereditary spherocytosis.

Diagnostic Tests for Hemoglobinopathies

  • Dithionite Solubility Test: Evaluates for sickle cell disease by observing the solubility of hemoglobin S.
  • Hemoglobin Electrophoresis: Separates different hemoglobin types based on their charge; useful in diagnosing sickle cell trait and other hemoglobinopathies.

Conclusion

  • Understanding the procedures, advantages, and implications of various hematological examinations is key to diagnosing and managing blood-related diseases effectively. Further study and practice are necessary to master these techniques and interpret their results.