AHG Testing

  1. IgG antigen-antibody binding
    IgG antibodies may dissociate from the RBC's
  2. Complement components binding
    • Once bound, complement components     
    • DO NOT
    • dissociate from the RBC
  3. PolySPECIFIC AHG reagent
    Contains antihuman globulin sera with specificity against IgG and complement.
  4. MonoSPECIFIC  AHG reagent
    Contains AHG sera against a single specificity; EITHER IgG or Complement
  5. PolyCLONAL reagent
    IgG antibodies derived from multiple cell lines. Molecules vary in specificity detecting multiple epitopes.
  6. MonoCLONAL Reagent
    IgM antibodies derived from a single  cell line. 

    All molecules are identical detecting a single epitope.
  7. If after adding CC's to negative reactions you obtain a weaker than expected reaction, what should be suspected at the problem?
    Improper washing due to a problem with the cell washer or tech method of washing.
  8. IAT
    • Used for:
    • antibody screens
    • ABID
    • Ag Typing
    • Weak D
    • crossmatching. 

    Usually will be performed using anti-IgG monospecific AHG reagent. 

    Rare to see polyspecific reagent used.
  9. DAT
    Direct Antiglobulin Test
    • Used for:
    • Transfusion Rx
    • HDN
    • AIHA

    • Performed with polyspecific AHG serum
    • *If a clotted sample is used (non-EDTA), than IgG may be reported only.
  10. DAT vs IAT
    • DAT:
    • In vivo sensitization
    • Tests for IgG bound to RBC's within the body

    • IAT:
    • In vitro sensitization
    • IgG is free in serum and is bound to the cells in the test tube
  11. DAT vs IAT
    • DAT:
    • In vivo sensitization
    • Tests for IgG bound to RBC's within the body

    • IAT:
    • In vitro sensitization
    • IgG is free in serum and is bound to the cells in the test tube
  12. Reasons for positive DAT
    • Poly & IgG = +
    • Could be due to WA, penicillin, cordblood, transfusion of ABO incompatible units

    • Poly, IgG, & Complement = +
    • Could be WA, Drug Ab, possibly ABO incompatible units

    • Poly & Complement = +
    • Could be CA, Drug antibody, WA in a lupus patient.
  13. Mixed Field
    Agglutinated RBC's seen among unagglutinated free cells

    May be seen in those recently transfused with a different blood type. (mf with IgG)

    Bone marrow transplants (mf with IgG)

    Chimeras

    A3 RBC's

    Women with unexptected IgG Ab who had a fetus that was antigen positive
  14. False Positives
    • 1. Autoagglutinable cells
    • 2. Bacterial contamination
    • 3. Saline contaminated by heavy metals or colloidal silica
    • 4. Dirty Glassware
    • 5. Over centrifugation or reading
    • 6. Ab's against preservatives in reagents
    • 7. Contaminating Ab's in the AHG reagent
  15. False Negatives
    • 1. Inadequate or improper washing of RBC's
    • 2. AHG reagent deterioration or neutralization
    • 3. AHG not added
    • 4. Patient/donor serum not added
    • 5. Pt/donor serum nonreactive due to bad complement deterioration
    • 6. inadequate incubation
    • 7. Cell suspension to week or too strong
    • 8. Over/under centrifugation
    • 9. Poor reading technique
Author
Kwalke12
ID
340740
Card Set
AHG Testing
Description
AHG Testing
Updated