(P-TS-9) An Outbreak of Anaphylactic Reactions to Group B Platelet/Plasma and its Possible Relation to Alpha-Gal-Associated Meat Allergy

Background/Case Studies: Alpha-gal syndrome (AGS) is a potentially life-threatening acquired meat allergy associated with Lone Star tick bites in the US and is increasing in prevalence in Maryland and Virginia. This entity came to attention following anaphylaxis to Cetuximab infusions. The allergen, Galactose-α-1,3-Galactose (alpha gal), is expressed in non-primate mammals and is antigenically similar to the B blood group antigen. Following the tick bite, individuals develop IgE sensitization to alpha gal. B blood group status offers some protection against development of the allergy. Many patients are not aware of the allergy, as symptoms are often predominantly gastrointestinal and occur hours after meat ingestion. Although not preferred practice, transfusion of plasma and platelets from group B donors is believed to be safe for group O recipients.

Study

Design/Methods: Three anaphylactic transfusion reactions were reported to the Transfusion Services of two hospitals within our institution’s health care system from November 2022 to February 2023. A retrospective chart review was performed for all three patients. Patients and/or family members were interviewed and serologic IgE levels to alpha-gal were measured in two of the three patients.

Results/Findings: All reactions met definitive criteria for an allergic reaction with severe hypotension and flushing and involved infusion of blood group B Plasma or Platelets to blood group O recipients. One reaction was acutely fatal, and one was associated with later demise related to intubation and aspiration pneumonia. The patients of the ultimately fatal cases had a cat allergy. A history of prior anaphylactic reactions to a unit of group O Red Blood Cells and a unit of group B Plasma in a previous admission was noted in one patient who had a history of 42 transfusions, where both instances of exposure to a blood group B component resulted in a reaction. All patients came from southern Maryland. Two patients had histories of tick bites, previously unexplained gastrointestinal complaints, and abnormal elevated levels of IgE to alpha gal (table 1).

Conclusions: Alpha gal IgE may be a cause of some anaphylactic transfusion reactions. Cat allergy may be a risk factor for severe reactions. Investigation of anaphylactic transfusion reactions should include a focus on ABO blood group incompatibility, and testing of IgE levels to alpha gal should be considered in all cases involving group B components to non-group B recipients. Avoidance of blood group B antigen containing components may be prudent in non-blood group B patients with established AGS. One case suggests that exposure to alpha gal may be possible though a non-blood group B component.

Importance of research: At outbreak of anaphylactic transfusion reactions has been observed in two Washington DC hospitals coincident with an increasing prevalence of AGS in Maryland and Virginia. Standard guidance on investigation of anaphylactic reactions does not focus on ABO incompatibility and advises investigation of IgA levels. The cases described suggest investigation of alpha gal IgE should be included in certain cases.