Example: Weak/Missing Reaction in the Forward Typing

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Example: Weak/Missing Reaction in the Forward Typing

Forward (Cell) Grouping
Reverse (Serum) Grouping
Anti-A
Anti-B
Anti-A,B
A1 Cells
B Cells
1+MF*
0
1+MF
0
4+
*MF= mixed field

Most probable ABO type: Group A
Possible Causes: Weak subgroup of A, notably A3. Weak results with mixed field reaction in the forward grouping could also 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.
Some strategies for resolution: Obtain patient history including previous ABO typing results and transfusion history. Antigen expression may be weakly expressed on red cells of persons with leukemia or other malignancies. Extended room temperature incubation of patient cells and reagent anti-sera can help to increase the reaction strength.