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Patient Blood Management

(P-PB-3) A Case of Unusual Development of Anti-E in Hemoglobin SC Without Known Exposure 

Sunday, October 20, 2024
12:00 PM - 1:00 PM  
Background/Case Studies: Approximately 61-78% of donors are negative for the E antigen, with significant differences across racial groups. Anti-E is commonly formed following sensitization after a blood transfusion or pregnancy. Rarely, it has been reported as a naturally occurring antibody. We present a rare case of the development of anti-E antibodies in a patient with Hemoglobin SC Disease without clear exposure. 

Study

Design/Methods: The frequency of naturally occurring anti-E is 0.1% in E antigen negative individuals and is usually best detected by patient plasma reaction with enzyme treated E positive red cells at room temperature.  Transfusion workup included pre-exchange type and screen and crossmatching by gel technique. Post positive screen, a thorough interview was conducted to rule out possible exposures. Different potential environmental and occupational exposures for this patient were discussed including sharing razors, toothbrushes, epilators, and other hygiene/beauty tools, and pregnancy.

Results/Findings: Approximately six months prior to this exchange, the patient had a positive screen with a nonspecific antibody. Her pre-exchange investigation revealed group B, Rh-positive phenotypically negative for E, JkB, C, S, K, and FyA and positive for e, c, FyB, JkA and s. Her antibody screening at this time was positive in two cell panels. Antibody identification resulted in an anti-E antibody.

Conclusions:

This patient is in her third decade of life and is transfusion dependent to manage her sickle cell disease (SCD) and recurrent vaso-occlusive crises so her exposure to red cell products is unavoidable. The American Society for Apheresis designates the need for red cell exchange (RCE) as a category I or II depending on a patient’s clinical history, including recurrent vaso-occlusive crises. 



Her blood was crossmatched to units phenotypically but not molecularly negative for C, E, and K antigens. Molecular blood typing allows for higher matching in this patient population. The American Society of Hematology recommends extended matching beyond the ABO and Rh systems to include Jka/Jkb, Fya/Fyb, M/N, and S/s at a minimum for all SCD patients.  



Despite rigorous investigation and a discussion of uncommonly considered blood exposures, no clear source was identified. Spontaneously occurring anti-E may be due to antigen cross reactivity and not a true immune red-cell antibody. Little evidence exists of the clinical significance of naturally occurring anti-E. Future pre-transfusion workup for this patient will require serologic crossmatch instead of electronic crossmatch, as she was already receiving E antigen negative blood products.  



Minimizing unnecessary exposure to blood products is the best way to prevent alloimmunization and transfusion reactions in this patient population. However, when RCE procedures are indicated, limiting exposure to blood products becomes difficult.