Alpha-gal sensitization and allergic blood transfusion reactions: a scoping review

Tick bites may expose individuals to a carbohydrate not found in humans, galactose-alpha-1,3-galactose (alpha-gal), including allergy to mammalian red meat or red meat-derived products presenting 2–6 hours after consuming the product plus positive alpha-gal specific IgE testing that may indicate alpha-gal syndrome (AGS). Anaphylaxis in group O recipients of group B blood products in the absence of other risk factors for allergic transfusion reactions could be transfusion-related alpha-gal syndrome (TRAGS); galactose-alpha-1,3-galactose (Gal-alpha1-3 Galβ1-(3)4GlcNAc-R) is similar to the B blood group antigen (Gal-alpha1-3(Fuc-alpha-1,2)Gal). To review scientific and grey literature with no date or language limit to: 1) describe characteristics of all known cases of transfusion-related alpha-gal syndrome (TRAGS) and hypersensitivity reactions to infusions of mammalian red meat-derived medical products besides blood components that may resemble TRAGS; 2) identify studies that explore possible relationships between alpha-gal sensitization and blood group that may be relevant to understanding TRAGS; 3) describe which clinical, laboratory, and epidemiologic parameters used to diagnose AGS food allergy are also appropriate to diagnose TRAGS; and 4) identify which diagnostic assays exist for AGS and how they are used for AGS and/or TRAGS. Using search strategies peer-reviewed by biomedical librarians we performed a scoping review of literature in five medical databases, charted in Microsoft Excel and Covidence software. Of 11732 studies imported for screening, 3858 duplicates were removed and 7874 papers were screened. Title and abstract screening excluded 7383 papers. Full-text screening excluded 380 papers. Of the included papers, 20/111 (18%) addressed risk for alpha-gal allergy by blood group and 18/111 diagnostics (16%). A comprehensive literature review showed a possible association between alpha-gal allergy and blood group. Further guidance is needed regarding potential clinical implications.