Exam revision May 23 - Transfusion science questions Flashcards
In what circumstances and for what reason would you perform a “Group and Save”?
In what circumstances and for what reason would you perform a “Group and Save”?
Group and save is the processing of a blood sample which determines patients blood group (ABO and RH) and screens for any potential antibodies. It takes around 40 minutes and no blood is issued. It is just in case the patient needs it for planned surgeries where there is an blood loss which is greater than expected.
Patients undergoing planned surgeries that may require transfusion, have samples for group and save taken at pre-admission clinics.
Basically, its a back up process.
What is the 2 sample rule?
What is the 2 sample rule?
This ensures that the blood bank have 2 distinct blood samples that have generated an identical blood group from both samples.
What is the difference between a cross-match and a “group and save”?
Both tests are necessary to request prior to a blood transfusion and G & S comes first.
Group and save is the processing of a blood sample which determines patients blood group (ABO and RH) and screen for any potential antibodies. It takes around 40 minutes and no blood is issued. It is just in case the patient needs it.
A serological cross match is used when an antibody has been identified in a patients plasma. It is the final step in pre-transfusion compatibility testing and involves mixing the patient and donor blood to see if immune reactions occur. A reaction would show in the form of agglutination.
An IAT is used for cross matching blood.
What does IAT stand for? Using a diagram explain the principle of an IAT test.
THIS ANSWER IS NOT FINISHED
IAT stands for indirect anti globulin testing or can be know as Coombs testing.
It can screen, determine a patient blood group, or screen the presence of IgG antibodies in plasma (smaller than IgM). Cells cannot agglutinate when suspended in saline*.
PRACTICE DRAWING THIS OUT AND FINISH THIS QUESTION OFF
What do we mean by the term “clinically significant antibody” in transfusion science? List some below.
A clinically significant antibody can be defined as one capable of causing accelerated destruction of a significant proportion of transfused cells, or one capable of crossing the placenta and causing haemolytic disease of the fetus and newborn.
Most significant antibodies are IgG antibodies rather than IgM. IgG antibodies typically react at or near body temperature (37 C) and are more likely to damage incompatible transfused red blood cells than antibodies that react best at lower temperatures.
Anti-D antibody in the RH system causes a lot of problems with HTR’s (haemolytic transfusion reactions) as it highly immunogenic.
Anti-c: made by patients without a c antigen.
Anti-C: rare but often found with anti-D.
Anti-e: rare and weakly immunogenic. There is only one AA difference between this and the Anti-E antibody.
Anti-E: less rare than anti-C but often found with anti-C. Clinically significant if Anti-E is reacting at 37 C.
Why should we NOT called the RH blood grouping system “Rhesus”?
A woman delivered a baby and needed a transfusion. She was given blood from her ABO compatible husband but had a severe reaction. When they looked at her plasma and tested it against donors. 80% of the donor blood agglutinated. Her blood group wasn’t named. It was declared “an interesting case”. However Landsteiner decided to test further and used a rhesus macaque monkey and injected it with rabbit and guinea pig blood cells. The rhesus monkey made an antibody to the rabbit and guinea pig cells. When this antibody was tested against human RBC’s, it caused agglutination or haemolysis with 85% of cases. It was thought that the woman who had reacted to the transfusion and the rhesus monkey were making an antibody to the same structure in the donor blood. This was later proved wrong.
It was the Rh antigen and the LW antigens (monkey reacted to) that they were reacting to. The LW antigen is abundant on RH D+ RBCs and the D antigen is the main antigen in the RH blood group system.
Give two reasons why RH is so clinically significant?
- Can cause anti-D severe HTR (haemolytic transfusion reactions).
- Can cause HDFN.
In an antibody identification panel, what happens when we “enzyme treat” red cells?
Name two antibodies that are enhanced by enzyme treatment and two antibodies where the reactions are no longer seen when enzyme treated panels are used.
Enzyme enhancement can be used to visualise the binding of IgG antibodies which are smaller than IgM antibodies.
The enzymes (papain or bromelain) are prteolytic so will break down particular substrates from the RBC (carbohydrate and protein residues) and these allow the RBCs to reduce their positive charge and come closer together, causing agglutination as IgG binds with antigens on the surface of the RBC.
Two antibodies which have their reactions enhanced with enzymes are the RH system and the Kidd system as the longer chains are removed, making the binding stronger.
Two antibodies which may disappear when using enhanced enzyme testing are anti-Fya (Duffy) and (MNS) due to the enzyme cleaving in a certain place which loses the antigen and prevents the antibody binding.
Why is it important to run both positive and negative controls on a DiaMed card?
What is the main difference between ABO and RH blood group systems?
ABO has naturally occurring antibodies and RH has not and only responds as a reaction to foreign material.
Which is the most common blood group anigen in the UK?
Blood group O
What is the difference between reverse and forward testing.
Forward group tests cells (anti-A, anti-B) and reverse group tests pt plasma (so would be ABO)
