Screening Cells & Antibody Panels Flashcards
What blood group are screening cells derived from?
Group O cells
Usually 3 screening cells, while panels are 10-20 cells
Wat blood group are screening cells derived from?
Group O cells
Usually 3 screening cells, while panels are 10-20 cells
When performing an antibody screen, what are the screening cells mixed with?
Antibody screening cells are Type O red cells that contain a distribution of antigens. They are mixed with the patient’s serum to determine if the patient’s serum contains any clinically significant antibodies.
Performing an antibody screen or a panel and testing the patient’s serum at various temperatures, with different enhancement medias, and with AHG is called what?
IAT - Indirect antiglobulin test
What is the autocontrol in an antibody panel?
When the patient’s serum is tested against their own red blood cells to detect presence of an auto antibody.
Explain how the Indirect Antiglobulin Test works.
We want to detect if there are antibodies in patient’s serum.
Reagent red blood cells (such as screening or panel cells) is added with patient serum. IN-VITRO sensitization of RBCs occur if antibodies are present.
AHG (polyspecific or monoclonal) is added to the sensitized red blood cells and incubated at 37C. AHG binds to the antibodies and cross links the red cells. This allows us to visualize red cell agglutination thus visualize a positive reaction.
What is AHG and what does it do?
AHG is anti-human globulin. It binds to antibodies or complement c3 (polyclonal) in order to visualize red cell agglutination by cross linking sensitized red blood cells.
What are checked cells and what is it’s purpose?
Checked cells are RBCs coated with antibody. They are added to a negative IAT or DAT rxn to ensure the AHG was working properly.
If IAT or DAT is negative, there should be free floating AHG in the mixture. AHG will bind to checked cells, causing agglutination and letting us know that the AHG is working properly.
Checked cells results should be [positive/negative?] if IAT or DAT is positive?
Negative.
AHG is bound to sensitized red cells, so it’s not free flowing in the mixture. Therefore checked cells wouldn’t have anything to bind to.
Explain the DAT test.
Want to find out if a patient’s red blood cells are sensitized in vivo.
Patient’s red blood cells are sensitized IN VIVO. Add AHG, which will bind to antibodies/complement coating the RBCs so we can visualize agglutination.
When is the DAT performed?
In cases where we want to see if a patient’s RBCs are sensitized in vivo: such as immune hemolytic anemia, or erythroblastosis fetalis (Rh- mother’s antibodies coating Rh+ baby RBCs)
When would you perform an IAT?
To screen an Rh- mother to see if there are antibodies in her serum that may attack the baby’s RBCs
Antibody screen, panel are both IAT methods
What could be the cause of a false negative IAT?
Inadequately washing of the cells prior to adding AHG!
Residual antibodies/globulins may neutralize AHG, rendering it ineffective
What is the prewarmed technique?
After proving no clinically significant antibodies are present in the IAT test, you want to eliminate reactions due to cold antibodies.
Warm serum and cells separately to 37c before mixing together again; or wash with warm saline prior to further testing.
What is antigen typing?
Patient must be NEGATIVE for the antigen to which the antibody is directed.
After antibody screen determines a clinically significant antibody,
Use patient RBCs, and type with antibody reagent sera. Pt should be negative.
Ex. Patient as Anti-E determined by panel, which means they do not have E antigen on their RBCs. Type Patient’s RED BLOOD CELLS with Anti-E reagent. Should be negative.
