ABO Grouping

• Forward grouping


  Testing of red cells for the presence of ABO antigens

  
• Forward grouping


  1. Commercially prepared antisera + patient's red cells

  2. Two Methods: slide method and tube method
• Reverse grouping


  Testing of serum or plasma for the expected ABO antibodies

  
• Reverse grouping


  Reagent red cells + patient's serum/plasma

  
• Characteristics of Routine Reagents Used for ABO Testing


  • Anti-A Reagent
  • Anti-B Reagent
• Anti-A Reagent


  • Monoclonal antibody
  • Highly specific
  • IgM
  • Clear blue-colored reagent (trypan blue dye)
  • Expected 3+ to 4+ reaction
  • Usually use 1-2 drops
• Anti-B Reagent


  • Monoclonal antibody
  • Highly specific
  • IgM
  • Clear yellow-colored reagent (acriflavine dye)
  • Expected 3+ to 4+ reaction
  • Usually use 1-2 drops
• Reagent A1 and B Cells


  • Human source
  • 4%-5% red cell suspension
  • Expected 2+ to 4+ reaction
  • Usually use one drop
• General rule: Always drop clear solutions first, RBCs second, to make sure you have added both source of antibody and antigen.
• ABO forward grouping/direct typing


  The ABO blood groups (A, B, AB, and O) represent the antigens expressed on the erythrocytes (red blood cells) of each group. ABO system is the only system in which there is a reciprocal relationship between the antigen on the red cells and the naturally occurring antibodies in the serum.
• ABO forward grouping/direct typing


  1. Reagent typing sera contains specific antibodies to A antigen and B antigen

  2. The procedure is based on the principle of agglutination of antigen positive red cells in the presence of antibody directed towards the antigens

  
• Specimen: EDTA-anticoagulated whole blood/red cell suspensions (2%-5%)

  
• Reagents


  • Anti-A (blue)
  • Anti-B (yellow)
  • Anti-A, B (colorless) → optional
• Slide Method


  1. Place 1 drop of anti-A on a clean, labeled glass slide

  2. Place 1 drop of anti-B on a separate clean, labeled glass slide

  3. Add to each drop of reagent on the slides 1 drop of whole blood or 2%-5% red cell suspension

  4. Mix the reagents and red cells thoroughly, using a clean applicator stick for each reagent

  5. Gently tilt the slide continuously for up to 2 minutes at room temperature (22°C-24°C)

  6. Read, interpret, and record the results of the reactions on all slides
• Tube Method


  1. Place 1 drop of anti-A in a clean, labeled test tube

  2. Place 1 drop of anti-B in a clean, labeled test tube

  3. Add to each tube 1 drop of whole blood or 2%-5% red cell suspension to be tested

  4. Mix the contents of the tubes gently and centrifuge all tubes for 15 seconds at 3,400 rpm

  5. Gently dislodge the cell button and examine for agglutination or hemolysis

  6. Read, interpret, and record the test results
• ABO Grouping Interpretation


  • O
  • A
  • B
  • AB
• Positive reactions characteristically show 3+ to 4+ agglutination by reagent ABO antibodies; reactions between test serum and reagent red cells are often weaker. The serum tests may be incubated at room temperature for 5 to 15 minutes to enhance weak reactions.

  
• ABO reverse grouping/indirect typing


  Reverse grouping (back type) is based on the detection of ABO antibodies in the patient's serum by using known reagent RBCs; namely, A1 and B cells.

  
• Specimen: Clotted/anticoagulated blood samples (serum/plasma)

  
• Reagents


  • Commercially prepared A1, A2 and B red cells (Note: The use of A2 cells is optional.)
  • Known A and Known B cells (2%-5% red cell suspensions → prepared in the laboratory)
• ABO Reverse Grouping/Indirect Typing


  1. Label two clean test tubes as A and B

  2. Add 2 or 3 drops of serum/plasma to each tube

  3. Add 1 drop of A group cells to the tube A and B group cells to the tube B

  4. Mix the contents of the tubes gently and centrifuge all tubes for 15 seconds at 3,400 rpm

  5. Examine the serum overlying the cell buttons for evidence of hemolysis. Gently resuspend the cell buttons and examine them for agglutination

  6. Read, interpret, and record test results

  
• ABO Reverse Grouping Interpretation


  • O
  • A
  • B
  • AB
• Reaction gradings vary from patient to patient.
• ABO Compatibility for Whole Blood, Red Blood Cells, and Plasma Transfusions


  • Recipient: Group A, Group B, Group AB, Group O
  • Donor: Group A, Group B, Group AB, Group O
• ABO compatibility


  Refers to the serologic compatibility between the ABO antibodies present in the recipient's serum and the ABO antigens expressed on the donor's red cells
• Universal donors


  Group O donors for RBC transfusions; Group AB donors for plasma transfusions
• Universal recipients


  Group AB recipients for RBC transfusions; Group O recipients for plasma transfusions
• Whole blood transfusions require ABO-identical donor units ONLY
• Universal donor for RBC transfusions is group O; universal donor for plasma transfusions is group AB.
• Universal recipient for RBC transfusions is group AB; universal recipient for plasma transfusions is group O.