ABO Typing Discrepancies
Antigens and antibodies specifically combine to form immune complexes. What term
refers to the antibody's attraction to a particular antigenic determinant (epitope)?
ANSWER- Affinity
Define: Affinity ANSWER- the strength of attraction that an antibody and antigen
possesses, which results in the formation of an immune complex.
Define: Avidity ANSWER- the strength of the bond between the antibody (paratope)
and antigenic determinate (epitope). This happens as a result of the immune complex
formation.
Define:van der Waals forces ANSWER- are the sum of attractive or repulsive forces
surrounding the red blood cell (RBC). These forces are important to creation of the
immune complex.
Define: Zeta potential ANSWER- is the overall ionic charge that surrounds the RBC. It
functions to repel RBCs from each other. Zeta potential must be overcome in order to
achieve agglutination.
Antigen ANSWER- In the postzone there is an excessive amount
Rbc membrane proteins
May or may not be considered an immunogen
Antibody ANSWER- In the prozone there is an excessive amount
These can be naturally occurring or produced after stimulation
They are soluble and found in plasma
There are 5 general classes
A patient's pretransfusion ABO grouping results are as follows:
Forward (Cell) Grouping
Anti-A= 4+
Anti-B=0
Anti-A,B=4+
Reverse (Serum) Grouping
A1 Cells=0
, B Cells=0
What is the MOST likely ABO group for this patient and what ABO typing discrepancy is
most descriptive of these findings? ANSWER- Patient is most likely Group A;
Unexpected reactions in forward typing
Forward (Cell) Grouping
Anti-A= 4+
Anti-B =0
Anti-A,B =4+
Reverse (Serum) Grouping
A1 Cells =0
B Cells =0 ANSWER- Category: Group l-- Discrepancies that are associated with
unexpected or missing/atypically weakened reactions in the reverse typing.
Most probable ABO type: Group A
Possible causes: Immunocompromised, age-related, transplantation, dilution,
technical/procedural error
Some strategies for resolution: Repeat testing with careful attention to accuracy or
repeat reverse typing with extended incubation at or below room temperature. Weak
ABO reactions can often be potentiated using extended incubation at or below room
temperature.
Forward (Cell) Grouping
Anti-A =1+ mf
Anti-B = 0
Anti-A,B = 1+mf
Reverse (Serum) Grouping
A1 Cells=0
B Cells 4+ ANSWER- Group II - Discrepancies that are associated with unexpected or
atypical reactions in the forward grouping, specifically mixed field reactions.
Most probable ABO type: Group A
Possible Causes: Weak subgroup of A, notably A3; weak results with mixed field
reaction in the forward typing could be due to the transfusion of large quantities of O
Red Blood Cells into a group A recipient, chimerism, or a group A patient transplanted
with group O stem cells.
Antigens and antibodies specifically combine to form immune complexes. What term
refers to the antibody's attraction to a particular antigenic determinant (epitope)?
ANSWER- Affinity
Define: Affinity ANSWER- the strength of attraction that an antibody and antigen
possesses, which results in the formation of an immune complex.
Define: Avidity ANSWER- the strength of the bond between the antibody (paratope)
and antigenic determinate (epitope). This happens as a result of the immune complex
formation.
Define:van der Waals forces ANSWER- are the sum of attractive or repulsive forces
surrounding the red blood cell (RBC). These forces are important to creation of the
immune complex.
Define: Zeta potential ANSWER- is the overall ionic charge that surrounds the RBC. It
functions to repel RBCs from each other. Zeta potential must be overcome in order to
achieve agglutination.
Antigen ANSWER- In the postzone there is an excessive amount
Rbc membrane proteins
May or may not be considered an immunogen
Antibody ANSWER- In the prozone there is an excessive amount
These can be naturally occurring or produced after stimulation
They are soluble and found in plasma
There are 5 general classes
A patient's pretransfusion ABO grouping results are as follows:
Forward (Cell) Grouping
Anti-A= 4+
Anti-B=0
Anti-A,B=4+
Reverse (Serum) Grouping
A1 Cells=0
, B Cells=0
What is the MOST likely ABO group for this patient and what ABO typing discrepancy is
most descriptive of these findings? ANSWER- Patient is most likely Group A;
Unexpected reactions in forward typing
Forward (Cell) Grouping
Anti-A= 4+
Anti-B =0
Anti-A,B =4+
Reverse (Serum) Grouping
A1 Cells =0
B Cells =0 ANSWER- Category: Group l-- Discrepancies that are associated with
unexpected or missing/atypically weakened reactions in the reverse typing.
Most probable ABO type: Group A
Possible causes: Immunocompromised, age-related, transplantation, dilution,
technical/procedural error
Some strategies for resolution: Repeat testing with careful attention to accuracy or
repeat reverse typing with extended incubation at or below room temperature. Weak
ABO reactions can often be potentiated using extended incubation at or below room
temperature.
Forward (Cell) Grouping
Anti-A =1+ mf
Anti-B = 0
Anti-A,B = 1+mf
Reverse (Serum) Grouping
A1 Cells=0
B Cells 4+ ANSWER- Group II - Discrepancies that are associated with unexpected or
atypical reactions in the forward grouping, specifically mixed field reactions.
Most probable ABO type: Group A
Possible Causes: Weak subgroup of A, notably A3; weak results with mixed field
reaction in the forward typing could be due to the transfusion of large quantities of O
Red Blood Cells into a group A recipient, chimerism, or a group A patient transplanted
with group O stem cells.
