What is a mixed field reaction in ABO grouping?
In a mixed field reaction, two different ABO groups are present in the same sample, causing discordant ABO typing. The front and back type results are not as predicted.
Which situations could cause mixed field agglutination when doing ABO testing?
Causes
- Transfusion of donor red cells.
- After an ABO mismatched stem cell transplant for example a blood group O stem cell donor and a blood group A stem cell recipient.
- Weak expression of the A or B blood group antigen.
- In some diseases, for example leukaemia.
What are the four ABO discrepancies?
The table that follows provides four useful categories. Weak, missing reactions (including mixed field) in the forward (red cell) typing. Unexpected reactions in the forward (red cell) typing. Weak or missing reactions in the reverse (serum) typing.
What is detected in ABO reverse typing?
The back/reverse type mixes an individual’s plasma with reagent RBCs positive for antigen A, and separate reagent RBCs positive for B antigen. The test also measures visual agglutination or lack of agglutination. Most ABO antibodies are immunoglobulin (Ig) M.
What causes a mixed field reaction?
One of the potential causes of mixed field reactions on ABO and Rh typing is the presence within an individual of a chimeric state or mosaicism4,5. A chimera is present when two or more distinct cell populations containing genetic material from more than one zygote exist within an individual.
Which subgroup of a typically gives mixed field reactions with anti-a reagent?
The two most common subgroups of A are A1 and A2. Both have strong reactions with anti-A reagent. Anti-A1 lectin is used to identify A1 and A2 cells.
How do you resolve ABO Rh discrepancies?
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.
What causes mixed field reaction?
What are the causes of Pseudoagglutination?
Pseudoagglutination in blood grouping and cross-matching, may be regarded as a very simple protein test; if it is absent, no inferences can be drawn, but, when it is present, it may be the first clue to the presence of a dysproteinemia, usually caused by a severe, chronic disease, probably cancer or infection.
Can Antim cause ABO discrepancy?
Anti M is considered a naturally occurring antibody that is usually active at temperatures below 37°C and is thus of no clinical significance. This antibody, if present in an individual, can lead to a discrepancy between forward and reverse ABO grouping and thus creates diagnostic difficulties for blood bank staff.
What causes false positive in ABO grouping?
Antibodies to preservatives, medications, disease states, Wharton’s jelly, and/or cross- contamination of reaction microtubes may cause false positive reactions.
What is the principle involved in the method of ABO typing?
Principle: The ABO and Rh blood grouping system is based on agglutination reaction. When red blood cells carrying one or both the antigens are exposed to the corresponding antibodies they interact with each other to form visible agglutination or clumping.
How do you get rid of cold reactivity in ABO tests?
Performing the ABO testing at warm temperatures or repeating the reverse grouping with reagent A1 and B cells that are negative for M antigen can eliminate the cold reactivity and help resolve the discrepancy. It is important to remember that we must not only recognize discrepant results, but also resolve them adequately.
What happens when the ABO type is not clearly determined?
When the ABO type has not clearly been determined, transfusion of universal donor red cells and plasma are necessary, thus depleting the supply of these products. It is important to know the possible causes of ABO discrepancies in order to develop algorithms and standard procedures to resolve them quickly.
Why is it important to know the possible causes of Abo discrepancies?
It is important to know the possible causes of ABO discrepancies in order to develop algorithms and standard procedures to resolve them quickly. This course will provide a general scheme for resolving ABO discrepancies and work through examples cases. Demonstrate knowledge and understanding of ABO testing and result interpretation.
Can mixed field reactions cause a discrepancy in ABO/Rh typing?
The patient’s blood type continued to appear as a mixed cell population during his hospital admission. There are a number of other scenarios in which mixed field reactions could cause a discrepancy in a patient’s ABO/Rh typing. Some weak subgroups of A (A 3) are known for giving mixed field reactions.
