Direct Antiglobulin Testing Flashcards
AB ID important steps
a
rule
negative
ID/AHG
1.) Autocontrol
2.) Rule out = no rxn…all sign ab
3.) all blood given must be negative (do phentoype)
4.) ID non ABO ab in system, AGH crossmatch compatible units
Indirect testing
in vitro
Direct testing
example
In vivo (example DAT)
AB screen test
what kind of test
what makes it indirect?
IAT
cells and plasma make it indirect test
What are other IAT tests?
a,c,w
Autocontrol, Crossmatch, Weak D
Direct Antiglobulin test
when is it ordered?
h
p
t
c
hemolysis present
positive autocontrol
transfusion rxn workup
cordblood eval
DAT
predicitive of?
what disease?
how many pts have pos DAT/no clin sympt?
hemolytic anemia by immune process 83% with symptoms
1-15% of pts have pos DAT and no clinical symtoms
Autocontrol
principle
what kind of test?
has?
in?
IDs?
indirect
has incubation step
in vitro
IDs presence in plasma
interpretations of autocontrol
positive
agg
could be?
t?
a?
c?
agglutination with ab
could be igG
transfused cells
auto immune
contaminant
Interpretations of autocontrol
negative
no?
DAT?
Not reactive with?
no agglutination at AHG
DAT likely negative for IgG
not reactive w old cells
DAT test
no?
in?
IDs?
Against?
no incubation
in vivo
IDs presence on cell
against Fc region of Ab
AHG is polyspecific….
antihumanglobulin (IgG and monoclonal)
anticompliment (monoclonal)
failure to add rgnt can cause false neg
Check cells
coombs
compliment
coombs: Anti-IgG
compliment: C3 affected
Positive C3b
hemolysis due to compliment
Positive IgG
immune process stimulation
Anti IgG positive
Anti C3D positive
WAIHA, HTR
Anti IgG Positive
Anti C3D Negative
WAIHA, HTR, HDN
Anti IgG negative
Anti C3D positive
CAD, PCH
Elution
does what to RBCs?
very large?
Cell is no longer viable after?
Whats best for ABO?
remove and ID ab coating red cells
very large aliquot of pt cells
cell is no longer viable after: acid/heat/freezing
(freezing best for ABO)
What process must be controlled in elution?
wash step must be controlled
expect a negative result
Adsorption
removes?
purposely?
removing autoab in order to ID underlying allo ab
purposely coat red cells w ab
Autoabsorption
used to?
When pt havent been?
use to remove autoab
used when pt hasn’t been transfused
Diffferential Absorption
used to?
used when a pt?
risks?
use to seperately ID Ab activity
used when a pt has been transfused
risk may accidently rule out high incidence ab
Controls for adsorption
expect what result for autoabsorption? (what is tested)
Allo absorbtion? test what?
expect negative result for autoabsorption - plasma w pt cells
alloadorption: test absorbed plasma with screen cells
expect neg agglut
Previous transfusion
mix?
ABO may show?
what will Elution show?
mix of self and non self
ABO may show mixed field
elution will show transfusion rxn
Mixed fields in the forwards type could mean?
pt was given O negative blood
Which is the best cell to remove auto ab in pt plasma using adsorption procedures?
pt cells
For the elution procedure, which step ensures that the washing was appropriate?
Testing the last wash with screen cells
