AB Detection & ID Flashcards
What is an antibody screen?
A test used to detect antibodies
Who are antibody screens used for?
- Transfusion paients
- Pregnant Women
- Patients who have had transfusion reactions
- Blood and plasma donors
What is the purpose of doing an IAT on a patient?
It’s used to detect unexpected antibodies in a patient’s plasma or serum using reagent RBCs (known).
What are reasons for an unexpected antibodies to appear?
- Found in addition to expected anti - A or Anti - B Ab
- RBC stimulation from transfusion or pregnancy
- May significant (IgG) or not significant (IgM)
Naturally occurring antibodies form as a result of…?
Exposure to environmental sources (e.g. pollen, fungus, and bacteria), which have structures similar to some RBC antigens.
Passively acquired antibodies appear as a result of…?
Produced in one individual and then transmitted to another via plasma - containing blood components (transfusion) or derivatives such as intravenous immunoglobulin (IVG).
Presence of autoantibodies means…?
Complicates detection of clinically significant antibodies
In blood banking we test “Blank” with “Blank”
Knowns (reagent RBC & reagent anti sera) with unknowns (patient serum and patient RBCs)
What are the phases incorporated into IAT?
Immediate spin (IM), 37C, and AHG
What phase in IAT can be done with or without potentiators?
The 37C incubation stage
What stage in IAT is where washing is done?
AHG phase
What is the purpose of Coomb’s Control Cells a.k.a. Check cells?
It’s used with negative reactions of AHG phase to ensure proper washing technique. The result of check cells should be positive. Negative is not good.
Where do antigen sources come from in IAT?
Commercial red cells
In IAT, where do antibody source comes from?
Patient’s serum/plasma
What materials are used in auto control?
Tests a patient’s serum with their own RBCs
If the auto control with a screen and its positive, what will need to be done?
May run a DAT (patient cells plus AHG) to detect in Vivo coating
A auto control is positive, running AC and DAT will determine what about the antibodies?
If the antibodies are directed against the patient’s cells or transfused cells (allo- or autoantibody)
How many phases are in DAT?
One phase (AHG)
In DAT, what is the antigen source?
Patient’s RBCs
In DAT, what is the antibody source?
Immunoglobulin attached to patient’s RBCs
What does DAT tell you about the patient’s RBCs?
If IgG or C3 coating the patient’s RBCs in Vivo
Describe the characteristics of a clinically significant antibody.
- Usually IgG
- Reacts best at 37 C and during AHG phase (IAT)
- These antibodies are associated with hemolytic transfusion reactions (HTRs) and HDFN.
In screening cells, which is more sensitive single or pooled donor group O cells?
Single donor O cells are more sensitive than pooled
In screening cells which blood group is used and why?
O cells are used… will come back later. I forgot her explanation.
What are your options to enhance an antigen - antibody reaction? Name 5.
- Saline - may only enhance if incubation 4 long time
- LISS - common choice
- BSA (bovine serum albumin)
- PEG, polyethylene glycol
- Proteolytic enzymes - destroy some antigens
Describe the use and limitations of saline
Use - Sensitive & cheap, and allows for shorter incubation time.
Limitations
1. Enhance cold autoantibodies
2. Some weak anti-K antibodies may be missed
3. Equal pans of plasma/serum and LISS are important
4. If ionic strength of a LISS procedure is altered, there is a decrease sing sensitivity of the test system
What is the use of BSA and its limitations?
Use: Affects second stage of agglutination, reduces …TBC
