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Blood Bank

Reagents

Think of Reagents as the essential ingredients in our blood bank “recipes” – each one has a specific job to do to ensure we get accurate results and keep transfusions safe!

  • We use Blood Grouping Sera (known antibodies) to find antigens on Patient RBCs
  • We use Reagent RBCs (known antigens) to find antibodies in Patient Plasma
  • We use Antiglobulin Sera (AHG) to detect the “invisible” binding of IgG/Complement to RBCs, either in vitro (IAT) or in vivo (DAT)

Here’s an overview of the Big Three reagent categories:

Blood Grouping Sera (The “Detectors”)

  • What They Are: Reagents containing known antibodies (primarily Anti-A, Anti-B, and Anti-D)
  • Their Job: To detect the corresponding antigens (A, B, D) on the surface of patient or donor Red Blood Cells during Forward Typing
  • How They Work: The antibody in the reagent specifically binds to the antigen on the RBCs, causing visible agglutination (clumping)
  • Key Players
    • Anti-A (Blue): Detects A antigen
    • Anti-B (Yellow): Detects B antigen
    • Anti-D (Clear/Colorless): Detects D antigen
    • Rh Control (Clear/Colorless): Crucial! Contains everything except the Anti-D antibody; must be negative to validate the Anti-D result
  • Source: Mostly highly specific monoclonal antibodies now
  • Bottom Line: These reagents establish the fundamental ABO/Rh type – the starting point for all compatibility testing

Reagent Red Blood Cells (The “Bait”)

  • What They Are: Suspensions of human Red Blood Cells with known antigen profiles
  • Their Job: To detect antibodies in patient or donor Plasma/Serum
  • How They Work: If the patient’s plasma contains an antibody, it will bind to the corresponding known antigen on the reagent RBCs, leading to agglutination or hemolysis (often requires the AHG phase for IgG antibodies)
  • Key Players
    • A1 Cells & B Cells: Used for ABO Reverse Typing to confirm the presence of expected anti-A/anti-B
    • Screening Cells (Set of 2 or 3, Group O): Used for the Antibody Screen to detect unexpected, clinically significant antibodies. MUST be Group O to avoid ABO interference. Come with an antigram detailing their antigen profile
    • Panel Cells (Set of 11-20+, Group O): Used for Antibody Identification when the screen is positive. Provide a variety of antigen patterns (detailed on the antigram) to help pinpoint the antibody’s specificity
  • Source: Carefully selected human donors
  • Bottom Line: These cells allow us to find and identify antibodies in the patient’s plasma, which is critical for selecting compatible blood. Watch those expiration dates!

Antiglobulin Sera (AHG / Coombs’ Serum) (The “Bridge Builder”)

  • What It Is: Reagent containing antibodies directed against human antibodies (Anti-IgG) and/or complement proteins (Anti-C3d)
  • Its Job: To detect red cells that have been sensitized (coated) with IgG or complement, especially when this coating doesn’t cause direct agglutination on its own
  • How It Works: The AHG antibodies bind to the IgG or C3d already attached to the RBCs, forming a “bridge” between adjacent coated cells, causing visible agglutination
  • Key Players
    • Polyspecific AHG: Contains both Anti-IgG and Anti-C3d. Used for initial DAT screen
    • Monospecific Anti-IgG: Contains only Anti-IgG. Essential for IAT procedures (Screen, ID, XM, Weak D) and DAT follow-up
    • Monospecific Anti-C3d: Contains only Anti-C3d. Used for DAT follow-up to detect complement coating
  • Source: Polyclonal (animal source) or monoclonal (hybridoma) antibodies, often blends
  • Bottom Line: AHG is crucial for detecting most clinically significant IgG antibodies (IAT) and investigating potential in vivo red cell destruction (DAT). Remember: Washing cells before adding AHG is critical to avoid false negatives! Check Cells validate negative results