ABO detection and ID Flashcards
The test used to detect antibodies is called an
antibody screen
Antibody screens are used for
Patients needing a transfusion
– Pregnant women
– Patients who have had transfusion reactions
– Blood(red cells) and plasma donors
Antibody Screen
Indirect Antiglobulin Test:
Uses the patient’s plasma or serum against reagent
RBCs to detect unexpected antibodies
Indirect Antiglobulin Test:
Unexpected antibodies
found in addition to the expected anti-A or anti-B antibodies
result of RBC stimulation (transfusion, pregnancy)
maybe
– Clinically significant (IgG)
– Not clinically significant (IgM)
Other Antibodies
Naturally occurring antibodies
may form as a result of exposure to
environmental sources (e.g., pollen, fungus, and bacteria), which have
structures similar to some RBC antigens.
Other Antibodies
Passively acquired antibodies
are produced in one individual and then
transmitted to another via plasma-containing blood components or derivatives
Other Antibodies
Autoantibodies,
when present, may complicate the detection of clinically
significant antibodies
In blood banking, we test knowns with
“unknowns”
KNOWN: UNKNOWN:
Reagent RBC + patient serum
Reagent antisera + patient RBCs
When detecting and/or identifying antibodies, we test the patient
When detecting and/or identifying antibodies, we test patient serum (unknown)
with reagent red cells (known)
Indirect Antiglobulin Test
Incorporates multiple PHASES of testing
IS = immediate spin (not required)
37oC = after incubation at 37oC with or without potentiators
AHG = anti-human globulin added (anti-IgG) after washing antibody/antigen reaction
Coomb’s Control Cells (aka Check Cells) =
used with negative reactions to ensure
proper washing technique = must be positive
“IAT”
Antigen Source
= commercial red cells
IAT
Antibody Source =
patient’s serum/plasma
Autocontrol
Tests a patient’s serum with their
own RBCs
(+) mean autoantibody
Autocontrol
Autocontrol is incubated with the
antibody screen (or antibody panel)
Autocontrol
The AC and DAT can help in determine if the antibodies are directed
are directed against
the patient’s cells or transfused cells (allo- or autoantibody)
Autocontrol
If a laboratory technician uses an autocontrol with a screen and it is positive,
the technician may run a DAT (patient cells plus AHG) to detect in vivo coating
If autocontrols (-)
then you have a alloantibody
DAT could be negative=
look up why
Direct Antiglobulin Test
antigen and antibody sources
Only incorporates 1 phase
AHG
Antigen Source = patient’s red cells
Antibody Source = Immunoglobulin attached to patient’s red cells
IgG or C3 coating patient’s red cells in vivo
Clinically
Significant
Antibodies
- Usually IgG
-React best at 37° C and
during the antihuman
globulin (AHG) phase
(indirect antiglobulin test
[IAT])
- Clinically significant
antibodies are associated
with hemolytic transfusion
reactions (HTRs) and HDFN
Performing
an Antibody
Screen
- Patient’s plasma or
serum is incubated with
screening cells
-After incubation, an IAT
is performed using AHG
reagent
- Want to detect any
IgG antibodies
Screening cells are
are single or pooled donor group O cells;
however, single-donor vials offer increased sensitivity
Screening Cells
group O cells are used so that
Group O cells are used so that anti-A and anti-B antibodies will not
react