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Understanding Immunohematology and Transfusion

Aug 22, 2024

Lecture Notes: Immunohematology and Transfusion Medicine

Introduction

  • Presenter: Wassi Manani, Medical Officer at Canadian Blood Services
  • Focus: National Immunohematology Reference Laboratory
  • Format: Combination of PowerPoint and chalk talk
  • Aim: Educational enhancement through visual aids

Case 1: 24-Year-Old Female for Outpatient Surgical Procedure

Blood Typing Results

  • Forward Typing:
    • Anti-A: 4+
    • Anti-B: Negative
  • Reverse Typing:
    • A1 cells: 1+
    • B cells: 4+
  • Rh Typing:
    • D reagent 1: 4+
    • D reagent 2: 4+
  • DAT: Negative (polyspecific reagent)

Key Questions

  1. Discrepancy Identification

    • Forward typing indicates Group A; reverse typing indicates Group O.
    • Discrepancy likely in reverse typing due to weak A1 cell reactivity.

  2. First Step in Discrepancy Resolution

    • Options: Pre-warm wash, review antibody screen results, increase incubation time.
    • Best approach: Review antibody screen results before taking further steps.

Resolving Forward and Reverse Typing Discrepancies

  • Forward Typing Discrepancies:
    • Extra antigen, missing antigen, mixed field agglutination.
  • Reverse Typing Discrepancies:
    • Extra antibodies, missing antibodies.
  • Common Issues with Group A:
    • Subgroups leading to weak anti-A reactions.

Antibody Identification: The Anti-M Antibody

Characteristics

  • Predominantly IgM and reacts at room temperature.
  • Clinical significance typically low unless reacting at higher temperatures (37°C).

Clinical Implications

  • Anti-M rarely causes hemolysis; typically causes delayed hemolysis.
  • In emergencies, cross-match compatible units can be issued despite anti-M presence.

Massive Hemorrhage Protocol Toolkit

Key Components

  • Multi-disciplinary team involvement (e.g., emergency, trauma, surgery).
  • Protocols tailored to institutional resources; review every three years.
  • Components of MHP include RBCs, plasma, platelets, potentially PCC if plasma not available.

Relevant Questions from Toolkit

  • Appropriate transfusion strategies during massive hemorrhage events.
  • Selection of blood products for patients based on age and gender (e.g., women <45 should receive O negative).

Case 2: 28-Year-Old Woman with AML

Blood Grouping and Transfusion Strategy

  • Patient initially A negative; sibling donor is B positive.
  • Standard practice: Transfuse based on current blood group (A negative) until transplant.
  • Post-transplant, switch to B positive for ongoing transfusions.

Discussion of Discrepancies Post-Chemotherapy

  • Forward typing shows A; reverse typing shows loss of anti-B.
  • Mixed field agglutination expected due to engraftment of new B positive cells.

Conclusion

  • Importance of understanding blood typing discrepancies and their resolution.
  • Need for clinical awareness in emergency situations regarding blood compatibility and patient safety.
  • Upcoming tiers (2 and 3) will cover more complex cases.

Full transcript