-
IgG antigen-antibody binding
IgG antibodies may dissociate from the RBC's
-
Complement components binding
- Once bound, complement components
- DO NOTdissociate from the RBC
-
PolySPECIFIC AHG reagent
Contains antihuman globulin sera with specificity against IgG and complement.
-
MonoSPECIFIC AHG reagent
Contains AHG sera against a single specificity; EITHER IgG or Complement
-
PolyCLONAL reagent
IgG antibodies derived from multiple cell lines. Molecules vary in specificity detecting multiple epitopes.
-
MonoCLONAL Reagent
IgM antibodies derived from a single cell line.
All molecules are identical detecting a single epitope.
-
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.
-
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.
-
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.
-
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
-
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
-
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.
-
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
-
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
-
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
|
|
