Transfusion practice blind spot in para-Bombay: A case report

Area of Science:

• Transfusion Medicine
• Immunohaematology
• Blood Group Serology

Background:

• The H antigen is crucial for expressing A and B antigens. Weak or absent anti-H activity can obscure true ABO blood group phenotypes.
• Standard blood grouping relies on detecting A, B, and H antigens and their corresponding antibodies.

Observation:

• A 59-year-old male with symptomatic anemia and upper gastrointestinal bleeding required transfusion.
• Previous blood typing identified him as O Rh D positive, with a history of successful transfusions.
• Current pre-transfusion testing revealed ABO discrepancies, pan-agglutination, and a negative direct Coombs test.

Findings:

• Further investigations, including anti-H lectin testing and saliva secretor studies, identified the patient's true blood group as para-Bombay B RhD positive.
• The para-Bombay phenotype lacks the H antigen precursor, leading to weak or absent expression of A and B antigens, mimicking blood group O.

Implications:

• Misidentification of the para-Bombay phenotype can lead to the transfusion of incompatible blood products, risking haemolytic transfusion reactions.
• This case underscores the importance of advanced serological testing to accurately identify rare blood group phenotypes, especially in patients requiring transfusions.
• Awareness and implementation of specific diagnostic protocols are essential for managing patients with rare blood group variants like para-Bombay.