Example: Unexpected Reaction in Forward Typing

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The page below is a sample from the LabCE course ABO Typing Discrepancies. Access the complete course and earn ASCLS P.A.C.E.-approved continuing education credits by subscribing online.

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Example: Unexpected Reaction in Forward Typing

Table 16. Example of Unexpected Reaction in Forward Typing.
Anti-A Anti-B A1 cellsB cells
Patient Results4+2+04+
Most Probable ABO Type: Group A
Possible Causes: A(B) phenotype, patient cells coated with IgG, acquired B antigen.
Some Strategies for Resolution: Review patient history. Retype with monoclonal reagents made from another clone or human polyclonal reagents if available; perform an antibody screen to detect autoantibody; perform a direct antiglobulin test (DAT); or wash patient cells and retest.
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. Since there is no B antigen present on the patient's red cell and there is anti-B in patient plasma, no agglutination should form.
Table 17. Results after Red Blood Cell Testing.
Patient Red CellPatient PlasmaResulting Reaction
A antigen (No B antigen) Anti-B Negative