Blood Banking (Immunohematology) Notes

Areas of the Clinical Laboratory

  • Chemistry
  • Hematology
  • Urinalysis
  • Coagulation
  • Microbiology
  • Blood Bank

Objectives

  • Understand the role of Blood Bank in patient care.
  • Familiarity with common Blood Bank tests.

Synonyms for Blood Bank

  • Transfusion Medicine
  • Transfusion Services
  • Immunohematology

Definition of Immunohematology

  • Immuno: Related to the body's defense against foreign substances or pathogens (antigens & antibodies).
  • Hematology: Study of blood.
  • Immunohematology: Study of antigens & antibodies in blood.
    • Purpose of Blood Bank Testing: Ensure a patient receiving blood does NOT recognize donor RBCs as foreign.

RBC Antigens

  • Proteins on the surface of red blood cells (RBCs).
  • Autoantigens: Antigens on an individual's cells.
  • Alloantigens: Antigens on donor cells.

ABO Blood Group Antigens

  • Type A: “A” antigen present.
  • Type B: “B” antigen present.
  • Type AB: Both “A” & “B” antigens.
  • Type O: Neither “A” nor “B” antigens.
  • Rh Antigens: Also known as “D” antigen.

Antibodies in Blood

  • Specialized immune proteins defending the body.
  • Serum antibodies: Circulate in plasma/serum.
  • Target and neutralize foreign substances (antigens), such as donor RBCs with complementary antigens.

ABO Antibodies in Blood

  • Two possible ABO antibodies:
    • Anti-A
    • Anti-B
  • Individuals possess ABO antibodies against the antigens they LACK (naturally-occurring).

Rh Antibodies in Blood

  • Anti-D: Most important Rh antibody.
    • Produced if:
    1. D antigen is absent.
    2. Exposure to D antigen (from pregnancy or transfusion).

Blood Bank Testing

  • Type & Screen:
    • Pre-surgery test to prepare for potential need for blood.
    • Type: Determines patient’s ABO & Rh (D) antigens (ABO/Rh Typing).
    • Screen: Detects unexpected antibodies in patient’s serum that may react with donor RBCs.

Type & Screen Testing

  • ABO Type Testing:
    • Rh Testing:
    • Positive: D antigen present.
    • Negative: D antigen absent.

Interpretation of Blood Bank Testing

  • Agglutination: Antibodies binding to antigens, causing clumping.
    • Test interpretation:
    • A: Agglutination (4+)
    • B: No agglutination

ABO and D Typing Procedure

  • Forward Type: Test patient cells with commercial Anti-A and Anti-B.
  • Reverse Type: Test patient serum with commercial A & B cells.

Antibody Screen

  • Purpose: Detect unexpected antibodies in patient plasma/serum.
  • Who Needs It:
    • Patients requiring blood transfusions.
    • Pregnant women/new mothers.
    • Suspected transfusion reactions.
    • Blood and plasma donors.

Antibody Screen Results

  • Positive: Unexpected antibodies present; further testing required.
  • Negative: No unexpected antibodies detected; no additional testing needed.

Positive Antibody Screen → Antibody Identification Panel

  • Follows a Positive Antibody Screen to identify specific unexpected antibodies through reaction patterns with panels of RBCs.

Crossmatch/Compatibility Testing

  • Results Interpretations:
    • Compatible: No agglutination; unit not harmful.
    • Incompatible: Agglutination; unit could cause harm (transfusion reaction).

Blood Types Compatibility

  • Group A Recipients: Can receive A & O.
  • Group B Recipients: Can receive B & O.
  • Group AB Recipients: Can receive AB, A, B, & O.
  • Group O Recipients: Can only receive O.

Blood Donation Compatibility

  • Group A Donors: Can donate to A & AB.
  • Group B Donors: Can donate to B & AB.
  • Group AB Donors: Can donate to AB only.
  • Group O Donors: Universal donors (A, B, AB, O).

Rh Compatibility

  • Rh Positive: Can receive Rh+ or Rh-.
  • Rh Negative: Can receive Rh- only (emergency policies vary for Rh+ depending on circumstances).