An ABO blood grouping discrepancy: Probable B(A) phenotype

Abstract In B(A) phenotype, an autosomal dominant phenotype, there is a weak A expression on group B RBCs. We herein report a case of a probable B(A) phenotype in a first time 20-year old male donor. The cell and serum grouping were done using tube technique and also with blood grouping gel card (Diaclone, ABD cards for donors, BioRad, Switzerland). The antisera used were commercial monoclonal IgM type. To check for the weak subgroup of A, cold adsorption and heat elution was performed. The cell grouping was A weak B RhD positive while the serum grouping was B. There was no agglutination with O cells and the autologous control was also negative. It was a group II ABO discrepancy with or without group IV discrepancy. Results for both the eluate and last wash were negative. Hence, the possibility of weak subgroup of A was unlikely. Blood grouping gel card also showed a negative reaction in the anti-A column. One lot of anti-A was showing ‘weak +’ agglutination while the other lot was showing ‘negative’ reaction with the donor RBCs by tube technique. There was no agglutination observed with anti-A1 lectin. Our case highlights the serological characteristics of a B(A) phenotype. This case emphasizes the vital role of cell and serum grouping in detecting such discrepancies especially in donors which can lead to mislabeling of the blood unit and may be a potential risk for the transfusion recipient if not resolved appropriately.