Ag-Ab Testing/Antiglobin Tests Flashcards
In terms of Ag-Ab testing in the lab, state 3 sources of Ags
- Patient cells
- Manufacturing cells, screening cells, panel cells, A and B cells
- Donor cells
In terms of Ag-Ab testing in the lab, state 3 sources of Abs
- Patient serum/plasma
- Manufacturing antisera
- Donor serum/plasma
In terms of Ag-Ab testing in the lab, patient cells are a ____ source of Ags
Unknown
In terms of Ag-Ab testing in the lab, manufacturing cells are a ____ source of Ags
Known
In terms of Ag-Ab testing in the lab, donor cells are a ____ source of Ags
Unknown
In terms of Ag-Ab testing in the lab, patient serum/plasma are a ____ source of Abs
Unknown
In terms of Ag-Ab testing in the lab, manufacturing antisera are a ____ source of Abs
Known
In terms of Ag-Ab testing in the lab, donor serum/plamsa are a ____ source of Abs
Unknown
Explain the difference b/w direct and indirect agglutination
DAT does not require incubation b/c the RBCs are already sensitized (came from patient’s arm)
Explain the principle of an antiglobulin test
Antihuman Abs bind to Fc portion of sensitizing Abs and form bridges b/w Ab-coated RBCs, resulting in visual agglutination
Abs found in polyspecific AHG reagent
Anti-IgG, anti-C3d, anti-C3b
When to use a polyspecific AHG reagent
Detection of IgG Abs
Abs found in monospecific AHG reagent
Anti-IgG, anti-C3d
When to use a monospecific AHG reagent
Differentiate reactivty when poly-AHG is positive
3 common blood groups capable of binding complement
- ABO
- Lewis
- Kidd
Coombs Check Cells
- Composition
Group O positive (D+) cells coated by manufacturer w/ anti-D (“sensitized cells”)
- Sensitization occurs by Ab or C’ coating RBCs vai complexing w/ Ag on RBC membrane
Coombs Check Cells
- Purpose of use
- Added to nonreactive tubes as a QC step;
- Used to verify that test system is valid (i.e., AHG was added, AHG not neutralized, proper washing of cells occurred)
Coombs Check Cells
- Expected results
MUST be positive, generally about 2+
- Free AHG can now bind to sensitized CCs
Coombs Check Cells
- Causes of unexpected results
Incomplete/improper washing
- start over w/ the entire test procedure
DAT
- Purpose of test
Detects in vivo sensitization of RBCs (IgG, C’)
DAT
- Sample/specific requirement
EDTA sample only
DAT
- Steps of procedure
- 2 drops of 5% cell suspension
- Wash 3x
- Add 2 drops AHG
- Spin and read
5a. If positive, end procedure
5b. If negative,add 1 drop CCs - Spin and read
IAT
- Purpose of test
Detects in vitro binding (IgG Ag-Ab complexes)
IAT
- Sample/specific requirement
Can use plasma or serum sample cells from EDTA or plain red top tube
