Serologic investigation and management of an antibody screen negative para-Bombay phenotype during pregnancy

Abstract Introduction/Objective Individuals with the Bombay and para-Bombay red blood cell (RBC) phenotypes express anti- H antibodies associated with acute hemolytic transfusion reactions. The rarity of compatible donor units creates unique logistical challenges. However, para-Bombay individuals have been shown to tolerate transfusion of non- Bombay RBCs without acute hemolysis. Therefore, accurate serologic identification and judicious management of blood products are crucial when planning to transfuse patients with anti-H. This is especially true during pregnancy, as early onset of labor and fetal distress can occur without warning. Methods/Case Report A 24-year-old gravida 2 para 1 (G2P1) at approximately 38 weeks gestation with the fetus in breech position was transferred to our hospital after anti-H antibodies were detected. Although our in-house antibody screen was negative on automated solid-phase red cell adherence (SPRCA) testing, manual tube testing revealed the presence of anti-H antibodies, and forward typing with Ulex europaeus lectin confirmed the absence of H-antigen. Further, Lewis B phenotyping and saliva neutralization demonstrated the presence of H-antigen in secretions, consistent with the O-para-Bombay phenotype. Finally, differential adsorption ruled out other clinically significant allo- antibodies. An external cephalic version (ECV) was initially planned since vaginal delivery carries lower bleeding risk than cesarean section (CS). Three frozen Bombay RBC units were obtained, with one possibly compromised before arrival. Four pre-warmed, cross-match compatible units of O-positive RBCs (non-Bombay) were also prepared. Acknowledging the unpredictability of ECV, the challenge of timing thawed frozen units, and the possibilities of massive hemorrhage versus wasting rare donor blood, our transfusion service ultimately recommended an elective CS with only one Bombay unit deglycerolized. The patient underwent an uneventful procedure without transfusion. Results (if a Case Study enter NA) NA Conclusion Overall, this case highlights key diagnostic and management considerations for patients with Bombay and para-Bombay phenotypes. First, automated SPRCA testing may provide false negative results for anti-H antibodies. Second, backup transfusion strategies for para-Bombay patients may include non-Bombay RBCs. Finally, the procurement, preparation, and use of rare donor blood products requires multidisciplinary clinical decision-making to optimize patient outcomes, especially for high-risk labor when unexpected acute bleeding events can occur.