Use: Measurement of IgE to galactose alpha-1,3-galactose (α-Gal sIgE) is used in the differential diagnosis of α-Gal mediated allergy.1,2 There are two distinct forms of this allergy: the first is an immediate-onset anaphylaxis observed following intravenous infusion of Cetuximab, a monoclonal antibody against epidermal growth factor receptor, and the second is a delayed-onset allergy or anaphylaxis that occurs several hours following consumption of red meat.3 Bites from certain ticks, such as the Lone Star Tick in the United States, have been implicated in the development α-Gal allergy. Furthermore, α-Gal may be helpful in elucidating the allergen responsible in patients initially diagnosed as having ‘idiopathic’ anaphylaxis or urticaria.

Limitations: Although the use of component IgE testing may enhance the evaluation of potentially allergic individuals over the use of whole extracts alone, it cannot yet replace clinical history and oral food challenge in most cases. Clinical history, patient’s age, and presence of comorbidities (such as atopic dermatitis) must be incorporated into the diagnostic determination.

If a food is tolerated in the patient’s diet on a regular basis, detectable food specific IgE does not confirm allergy to that food. In population studies, many individuals produce IgE to α-Gal but do not have allergic symptoms.7 If allergy to a specific food is suspected based on clinical history, an undetectable food specific IgE does not exclude allergy to that food.

Alpha-gal allergies are similar to pork-cat syndrome. Pork-cat syndrome usually elicits an immediate allergic response, while a true α-Gal allergy typically features a delayed allergic reaction of 3 to 8 hours after ingestion of the allergen.8

Total IgE levels are of value in assessing potential α-Gal allergy because some cases are non-atopic and have low total IgE.9,10

Collection Details:

Collection Instructions:

Specimen: Serum

Volume: 0.5 mL

Container: Red-top tube or gel-barrier tube

Collection: If a red-top tube is used, transfer separated serum to a plastic transport tube.

Storage: Instructions:Room temperature