Possible causes of an ABO discrepancy due to extra plasma reactivity include ABO subgroup, cold reactive alloantibody, cold reactive autoantibody,
antibody to reagent constituent
, transfusion of non-ABO-group–specific plasma components, infusion of IVIG, and post–stem cell transplant status.
What are the causes of ABO discrepancy?
ABO discrepancies may be due to
clerical errors or technical problems with a sample or during testing
. Intrinsic problems within red cells or plasma may also lead to ABO discrepancies. Although many advances have been presented for ABO blood grouping, discrepancies still occur.
When do ABO discrepancies occur?
An ABO discrepancy occurs
when the results of forward and reverse typing do not match
. The reactions shown are described below in descending order: Patient red cells with reagent anti-A: negative reaction. Patient red cells with reagent anti-B: 4+ agglutination.
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 are the different ABO discrepancies?
Group
I – Discrepancies
that are associated with unexpected reactions in the reverse grouping. Group II – Discrepancies that are associated with unexpected reactions in the forward grouping. Group III – Discrepancies between forward and reverse grouping caused by protein or plasma abnormalities.
How do you fix ABO 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 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 is forward and reverse typing?
Forward typing-
A blood typing procedure whereby patient red blood cells are mixed with Anti-A and Anti-B reagents
. … Reverse typing – A blood typing procedure where patient serum is mixed with reagent A cells and reagent B cells. The results should be the opposite of forward typing.
How do you resolve acquired B?
Patient Results
This ABO discrepancy can be resolved by
testing patient plasma with patient red blood cells
. Patients who are truly group A, without any true B antigen, will demonstrate a negative auto control.
Does O blood group have H antigens?
If a person has blood group O,
the H antigen remains unmodified
. Therefore, the H antigen is present in the highest amounts in blood type O and in the least amounts in blood type AB.
What is a subgroup in blood bank?
As with other blood group systems, the ABO system has variant phenotypes with a genetic basis. The term “subgroup” refers
to phenotypes with variations in the structure or number of the A and B antigens
, related to variations in the enzymes that produce them.
What is anti c blood?
Anti-c antibody develops
in individuals sensitized through previous exposure
and is associated with acute and delayed hemolytic transfusion reactions as well as hemolytic disease of the newborn (HDN). Most antibodies produced against Rh antigens are of the immunoglobulin (Ig) G type.
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
.
What is acquired B phenomenon?
Acquired B phenomenon occurs
when the bacterial deacetylase converts N-acetylgalactosamine to α-galactosamine
, which is quite similar to the B-antigen immunodominant sugar, galactose. This variety of acquired B is the ‘deacetylase type' and is observed in the setting of A1 red cells (RBCs) only.
How do we determine blood type?
The test to determine your blood group is called
ABO typing
. Your blood sample is mixed with antibodies against type A and B blood. Then, the sample is checked to see whether or not the blood cells stick together. If blood cells stick together, it means the blood reacted with one of the antibodies.
What should be the first thing that a medical technologist can do when there is an ABO discrepancy?
- Retest the sample first, using a different method, if available.
- Check for technical or clerical errors.
- Remember that the weakest reactions are usually the ones that are in doubt.
- Complete the antibody screen and note positive reactions.
