ABO discrepancies may be due to clerical errors or technical problems with a sample or during testing. How can ABO discrepancy be resolved? In this situation, the discrepancy can be resolved by washing and re-suspending patient RBCs in saline, followed by repeat forward typing with anti-A and anti-B.
Full Answer
How do you test for ABO discrepancy?
Determining the ABO group requires both red blood cell (RBC) antigen typing for A and B (forward type) and testing for anti-A and anti-B in the plasma (reverse type). An ABO discrepancy exists when the result of an ABO RBC typing, or … Patient samples are routinely typed for ABO prior to transfusion.
What are the possible causes of Abo discrepancies?
They are due to technical errors, problems with the patients RBCs, plasma or both ABO discrepancies can be classified into the following categories: Group 1: problem with reverse grouping (unexpectedly weak / absent) = weakly-reacting / missing antibodies in patient’s serum
What does an ABO typing discrepancy mean?
An ABO typing discrepancy means that the interpretations of the red cell (forward) testing do not agree with the serum (back) testing.
What is the ABO discrepancy in blood bank?
One of the most common complications encountered in Blood Bank is the ABO discrepancy, where the forward type (or front type) indicates one ABO blood type and the reverse type (or back type) indicates a different ABO blood type. This has to be resolved before type-specific blood can be given to the patient.
What are the different methods of ABO testing?
These vary from slide testing to tube testing and microplate testing.
Why is it important to diagnose multiple myeloma?
The patient’s diagnosis is very important in resolving discrepancies as patients with malignancies are often treated with chemotherapy that causes im-munosuppression, giving antibodies a weak appearance. Patients who are diagnosed with multiple myeloma will usually have large amounts of proteins present, and these will cause rouleaux formation or abnormal aggregation of the red cells, which can mask true agglutination. To correct this problem, cell suspensions must be carefully washed, and the serum sample should be diluted with saline to the point where rouleaux is no longer present. 2
What blood group is used for back typing?
Within the “A” blood group are several subgroups which may at times react with the A1 used in back typing, resulting in a discrepancy. Most of the time it will be an A2 or an A2B individual. Typing the cells with anti-A1 lectin ( Dolichos biflorus) will help resolve this problem.
What is the phenotype of Bombay?
A phenotype that is rarely encountered is the Bombay or Oh phenotype. The cells of a Bombay individual will forward and back type as a group O, because they lack the antigens A, B and H , and have anti-A, anti-B and anti-H antibodies. While a discrepancy does not appear at first, the problem surfaces when the patient’s serum is tested against O cells. Since anti-H is present they will agglutinate these cells.
What happens when Tn activated cells are encountered?
Acquired A occurs when Tn activated cells are encountered because of a somatic mutation which results in some hematopoietic cells incapable of synthesizing certain oligosaccharide side chains entering the circulation in the Tn polyagglutinable state. The Tn and A cells have the end sugar N-acetyl-galactosamine and will be agglutinated by the anti-A antisera. The use of proteolytic enzymes in this situation would be beneficial as this would degrade the acquired A antigen. 5
What is acquired B?
Another serological problem occasionally encountered involves the acquired B and acquired A antigens. The acquired B problem is encountered when bacterial enzymes deacetylate the A1 antigen, causing it to react weakly when tested with anti-B antisera. Usually associated with patients diagnosed with carcinoma, this problem is not commonly seen as most blood banks use monoclonal reagents, and acquired B may or may not react with a monoclonal anti-B.
Can cold autoantibodies be used for back typing?
In this situation, pre-warming of all reagents and blood samples used will resolve the problem. There are other antibo dies that react at room temperature, which may bind with the cells used for back typing if these cells contain the corresponding antigen. These include antibodies to the M and P1. Once all other factors have been ruled out it may be necessary to resolve the discrepancy by testing with various lot numbers of back typing cells to see if different reactions are obtained, and testing screening cells or even a panel of cells at room temperature to arrive at an antibody specificity.
What temperature can cause agglutination?
Incubation at 4°C requires the use of auto-controls or control O+ cells as incubation at cold temperatures can cause agglutination due to activation of commonly-occurring cold-agglutinins such as anti-I, which react with all adult RBCs
How long to incubate a rbc at room temperature?
Incubate at room temperature for 15-30 minutes. Incubate at 4°C for 15 minutes. Incubation at 4°C requires the use of auto-controls or control O+ cells as incubation at cold temperatures can cause agglutination due to activation of commonly-occurring cold-agglutinins such as anti-I, which react with all adult RBCs.
How to treat BGSS?
For patients with BGSS: Wash red cells and suspend them in saline instead of plasma. For patients with low-incidence antigens which may react with antibodies in the antisera: Change lot numbers; the new lot should not have the low-incidence antibody and thus will not non-specifically react with the red cells.
What is the presence of other allo-antibodies to high-incidence antigens reacting with?
Presence of other allo-antibodies to high-incidence antigens reacting with reagent cells
What is the B phenotype of E. coli?
Polysaccharide of the E. coli O86 subtype (often associated with colorectal cancer) Can cause an “acquired B” phenotype in group A individuals due to adsorption of a B-like polysaccharide from E. coli. B-line polysaccharide reacts with human source anti-B.
Can BGSS neutralize antisera?
BGSS in patient’s serum can neutral ise antisera used in forward grouping
Which disease can weaken antibody expression?
Antigen expression often follows disease course (gets stronger if disease enters remission) Diseases which can weaken antibody expression: CLL or myeloma which can be associated with hypogammaglobulinaemia. Resolve by running protein electrophoresis or demonstrating low IgG, IgA and IgM.
What is acquired B antigen?
Acquired B antigen. a. Patients with acquired B antigen will have results typical of a patient with A type blood but will also have a 1+ or 2+ reaction in the forward typing with anti-B. This can be caused by a type of gastrointestinal disease where bacteria change the A antigen sugar to appear like B antigen.
Why is blood banking important?
An important part of blood banking is knowing how to deal with unexpected results. Discrepancies in the blood bank are common and knowing how to solve them is critical. They can be caused by patient RBCs, patient serum, an underlying condition, human error, or a number of factors. Blood cannot be released if there is an unresolved discrepancy.
Can blood be released if there is an unresolved discrepancy?
Blood cannot be released if there is an unresolved discrepancy. Here are a few common discrepancies to be aware of. 1. Patient has A2 RBCs and anti-A1. a. Remember not all people with A2 blood make anti-A1, in fact most don’t.
What to do if DAT is positive?
If the DAT is positive due to IgG, treat the cells with EDTA Glycine-Acid (Gamma EGA Kit) to remove any bound antibody and then repeat the Rh grouping. Report result.
What is a 6.3.2.1 patient history check?
6.3.2.1 Perform patient history check to determine if the patient has been transfused with non-group specific RBC components in the past 3 months or received an ABO-mismatched stem cell or bone marrow transplant.
What is 6.2.1.1?
6.2.1.1 Perform patient history check to determine if the patient has been transfused with non-group specific RBC components in the past 3 months or received an ABO-mismatched stem cell or bone marrow transplant.
What is a history check?
history check to obtain diagnosis, transfusion history, obstetrical history, transplantation history and current medications. It may be necessary to consult with other facilities to obtain a thorough patient history.
Mixed Field Reactions
- These are not ABO discrepancies, but refer to a specific reaction grade with two distinct sets of reactions
- Prior transfusion (e.g. group O transfusion to non-O recipient)
- ABO incompatible stem cell transplant
- Large feto-maternaal haemorrhage (very rare)
Technical Errors
- Sample collection from the wrong patient
- Labeling errors
- Failure to add reagents
- Failure to add sample
Abo Antigens in Disease States
- Disease states can alter the expression of ABO antigens / antibodies
- Diseases which can weaken antigen expression:
- Diseases which can weaken antibody expression:
- Polysaccharide of the E. coli O86 subtype (often associated with colorectal cancer)
Group 1 Discrepancies
- Group 1 discrepancies are the most common
- They may be seen in:
- Resolution
Group 2 Discrepancies
- Causes
- Resolution