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What is the importance of performing antibody screens?
Results show that the specimen contains no detective antibodies that are reactive with screening cells
Can detect clinically significant antibodies causes RBC destruction, HDFN, transfusion reactions, and death
Helps recognize antibody so an ID panel can be performed in order to select donor units with a negative corresponding antigen to create a safe transfusion
important in prenatal care, HDFN, HTR, and detecting autoimmune diseases
What is the question that performing an antibody screen answers
Are there any antibodies in serum or plasma that could cause a problem when the persons serum or plasma is mixed with donor red cells
Performed in pre-transfusion testing
Describe the antibody screen procedure
3 tubes, 2 drops of serum or plasma, 1 drop screen cells, 2 drops LISS for enhancement. Incubate ten minutes at 37, SRR
Wash cells and add two drops of of anti-igG , SRR for the IgG phase
add check cells to any negative reaction this should be positive to confirm. If it is negative, the test procedure is invalid and should be repeated
List the frequencies in the US population for type O blood
45 in Europeans, and 44 in African Americans
What is the purpose of QC
Provide feedback on testing reproducibility and reliability, consistent performance, need for calibration or reagent changes
QC helps to validate the test system
In an antibody screen, why use group O red cells against the patient serum or plasma
group O does not have any antigens on red cells surface so if the antibody screen is positive it wont be because of abo antibodies which would be present if it was any other blood type
how is an antibody screen performed?
Serum or plasma is added to RBC from 2-4 group O persons that could be targets of significant RBC antibodies performed in all phases (IS, 37, AHG)
In gel testing for antibody screens, microtubes are used. Describe what positive and negative results look like and why
Negative reactions are when the red cells settle at the bottomed and are able to pass through the Igg coated gel separator
Positive reactions are when the red cells settle at the top and are not able to pass through the Igg coated gel separator meaning that it Upon centrifugation, the Anti-IgG in the gel binds to those coated cells and traps them.
Frequency in US population of type A
40 Europeans, 27 African American
What does a positive and negative QC result mean
Positive result means that a test can detect target, Negative means that it does not detect a non target.
In blood donation, what other antibodies should the donor be negative for that is not abo/rh or other clinically significant antibodies
HIV, HEP C, HEP B core antigen, Trypansoma, West nile, Zika, babesia, syphilis, etc
What are the three methods of performing antibody screens
tube, gel, solid phase
Describe the solid phase antibody screen method and what a positive and negative results looks like
Microplates with rbc antigen are coated onto wells surface and patient serum is added.
If the antibody binds to AHG coated RBC, it creates a uniform layer like a filled in circle
If it is negative and the antibody is not bound, then the cell button will stay in the center of the circle
Frequency of type B in US population
11 Europeans, 20 African Americans
What is the temperature of stored reagents and the heat block?
Temperature of stored reagents is 2-8 degrees celcius
Heat block is 37 degrees Celsius
Reagents and blood components are stored separately to prevent confusion and mixups as well as contamination
What are the clinically significant antibodies that could be detected in the antibody screen
Duffy, kell, kidd, P, Mns, Rh
What is the criteria for performing antibody screens (what should the result be)
Reacting all 37 degrees, the findings from the antibody screen should be on the unit label, and in order for transfusion the antibody screen should be negative for clinically significant antibodies
What kind of gel is used in gel method
Dextran acrylamide
Frequency of AB in US population
4 Europeans, 4 African Americans
What is the difference between primary antibody response and secondary or amnestic response
Primary response is slower, weaker, and the initial reaction to antigen and its usually Igm first and the IGG, these are naive cells
Secondary response is the memory cells and it is faster and stronger response with stronger antibody concentrations and its mainly IgG it has an increased affinity for the antobody because it has stored memory of the antigen and initial exposure
If an antibody screen is negative, does this mean the person has no antibodies or no clinically significant antibodies
No. This means that there is no detectable antibodies. There could still be low incidence antibodies or others
What does a positive and negative result LOOK like in an antibody screen?
A positive result is the presence of agglutination or hemolysis
A negative result is the absence of agglutination of hemolysis
Describe the antisera that blood donors are typed with
RBC tested with anti a and anti b and anti d for rh factor and the plasma is tested with a cells and b cells
List the pre-transfusion testing and results that need to be performed before a unit is ready for transfusion or acceptable for issuing
Confirm ABO/Rh, ensure sample is valid (labled correctly, not hemolyzed, was stored at the right temperature), negative antibody screening antibody ID, and compatible cross match
Testing performed at all phases, review of donor history and eligibility, documentation
Elution
Elutions are performed when the DAT is positive, it dissociated and removes the antibody to recover the bound antibody into a useable liquid form
It breaks down the antigen-antibody complex
useful for concentration/purification of antibody, can detect weakly expressed antigen, phenotyping, and ID weakly reactive antibodies
Detects IgG sensitized antibodies