In order to provide a systematic approach for problem-solving, ABO discrepancies are generally divided into four categories (Table 6). To determine the most likely category, the laboratory professional must look at the strength and specificity of the reactions in the context of the patient history and findings. The laboratory professional then selects the “most probable” hypothesis based on this initial data. The table that follows provides four useful categories. In addition to the table, common causes of ABO discrepancies are bulleted below:
- Cold or room temperature reactive allo- or autoantibody reacting with antigens on the reverse grouping cells
- Excess serum protein resulting in rouleaux formation
- Passively transfused antibody in the transfusion of plasma components or the administration of IVIG
- Passenger lymphocyte syndrome associated with solid organ transplant
- Hematopoietic stem cell transplant
- Subgroups of A producing anti-A1
Table 6. ABO Discrepancy Classifications.| Category | Possible Associated Patient Scenarios |
| Weak, missing reactions (including mixed field) in the forward (red cell) typing. | - ABO subgroups
- Weakened antigens in chronic disease
- Transfusion of non type-specific RBCs
- Transplantation
- Chimerism
|
| Unexpected reactions in the forward (red cell) typing. | - RBCs coated with IgG
- Unwashed patient cells (excess protein resulting in rouleaux formation)
- Transplantation
- Acquired B antigen
- A(B) or B(A) phenotype
- Chimerism
- Polyagglutination
|
| Weak or missing reactions in the reverse (serum) typing. | - Immunocompromised patient
- Age related (infants and elderly patients)
- Transplantation
- Dilution
|
| Unexpected reactivity in ABO reverse typing. | - Cold or room temperature reactive allo- or autoantibody reacting with antigens on the reverse grouping cells
- Subgroups of A producing anti-A1
- Excess serum protein resulting in rouleaux formation
- Passively transfused antibody in the transfusion of plasma components or the administration of IVIG
- Passenger lymphocyte syndrome associated with solid organ transplant
- Hematopoietic stem cell transplant
|
