11 Antibody Screening & Identification

Cards (44)

  • Antibody screening identifies the specificities of antibodies causing positive serological crossmatch
    • SPECIMEN: Serum + screening cells
  • Antibody screening is a key process in pre-transfusion compatibility testing.
    • It is one of the principal tools for investigating potential hemolytic transfusion reactions, HDN, and immune hemolytic anemia
    • Detects alloantibodies, which are antibodies against someone else’s red blood cells.
  • Autoantibodies may complicate detection. If there is presence in their plasma or serum, it complicates detection because it does not mean that it will cause hemolytic reaction.
  • Cause of Hemolytic reaction are antibodies of patient that targets the donor or someone else's red blood cells.
  • Autoantibodies can cause positive screening
  • Tube technique is routinely performed.
    • Recipient serum + known RBCs (screening cells)
    • IS+37°C+AHG
    • Enhancement media may be used
  • Enhancement media may be used in tube technique such as LISS, BSA, PEG, in order to facilitate antigen-antibody binding
  • In tube technique, there is hemolysis or agglutination in any phase.
    • In order to observe hemolysis or agglutination, we have to use serum as a plasma
  • RBC reagents
    • 2-5% in preservative diluent
    • Packaged in sets of 2-3 cells with varied antigen expression.
    • Accompanied by antigen profile sheet
  • Antigen profile sheet is used for basis or guide in antigens present in screening cells
  • 22% Albumin is an enhancement media that reduces zeta potential
  • Zeta potential is the net negative charge present in red blood cells membrane.
    • Works to repel other red blood cells from one another to avoid clumping during circulation
    • Makes your red blood cells comes together so that they will be agglutinated by your antibodies
  • Low ionic strength solution is an enhancement media which is a glycine in an albumin solution.
    • It increases uptake of antibodies onto RBC surface
  • Polyethylene Glycol is an enhancement media that removes water in test system thereby concentrating any antibodies present
    • Makes the RBC surrounding hydrophobic so that they can easily take up the antibodies
    • Not appropriate for recipients with increased plasma proteins
    • Generally more sensitive than LISS and albumin
  • Be very careful in using PEG enhancement media because it can cause non-specific aggregation of cells (centrifugation after 37°C is omitted) and has a high chance of producing a false agglutination
  • AHG reagents brings the non-agglutinating antibodies together.
  • In order to visualize antigen-antibody binding, we add AHG reagents for us to see the presence of non-agglutinating antibodies in reaction vessel
  • Polyspecific AHG
    • Polyvalent or broad-spectrum Coombs serum
    • Components:
    • Anti-IgG
    • Anti-C3/C4 or Anti- C3d/C3b or Anti-IgM
  • Monospecific AHG
    • Components
    • Anti-IgG or Anti-C
  • Coombs control cells are basically red blood cells with attached anti-D antibodies in their D antigen
    • D(+) RBCs coated with anti-D
    • Used to verify if the negative AHG is valid
  • Agglutination or hemolysis in any of the phase
    • NEGATIVE (0) = the patient has no antibodies against the antigens present in the screening cells
    • POSITIVE (+1 to +4) = complete hemolysis (+4)
  • IgM antibody allows reaction of cold reacting antibodies, which is detected in IS phase
  • Polyspecific AHG detects IgM antibody if the AHG contains anti-complement activator
  • IgG antibody is detected in 37°C/AHG phase
  • In autocontrol,
    • (+)Ab screen; (-) Autocontrol = Alloantibody
    • (+)Ab screen; (+) Autocontrol = Autoantibody and/or Alloantibody
  • There is single antibody if reaction is in same phase and same strength
  • There is multiple antibody if reaction is in more than 1 screening cell
  • This table shows that the reaction is caused by alloantibodies
  • This table shows that the reaction is caused by alloantibodies and autoantibodies
  • Mixed field agglutination indicates presence of potent hemolysins, specifically Anti-Sda, Anti-Lua/Anti-Lub
  • Possible causes of reaction:
    • Caused by single Alloantibody
    • Two alloantibodies, antigens present only on cell II
    • Probably IgG antibody
  • Possible causes of reaction:
    • Multiple antibodies
    • Single antibody showing dosage effect
    • Probably IgG antibody
  • Possible causes of reaction:
    • Multiple antibodies
    • Single antibody showing dosage effect
    • Probably IgMAnti-N, Anti-M
  • Possible causes of reaction:
    • Multiple antibodies
    • Potent cold-reacting antibody that binds complement
    • Probable mixture of IgM and IgG
  • Possible causes of reaction:
    • Single antibody, antigen present in both cells
    • An antibody against a high frequency antigen
    • Weak, cold-reacting antibody that binds complement
  • Possible causes of reaction:
    • Warm-reacting allo/autoantibodies
    • Probably IgG antibodies
    • Transfusion reaction
  • In antibody identification, 11-20 Group O cells with varied antigen expression is used as reagents
  • A profile sheet specifying the antigens on each cell and providing a place to record reactions accompanies each panel.
    • (+) Sign indicates the presence of the antigen
  • Strength does not indicate significance, only the amount of antibody available to participate in the reaction
    • Different reaction strengths = Multiple antibodies or Antibodies showing Dosage effect
  • IgM antibody is clinically insignificant in IS phase