The Metabolomics of Anaphylaxis to Immunotherapy

Anaphylaxis is defined as a serious allergic reaction mediated by IgE that is often difficult to diagnose due to the wide heterogeneity of clinical manifestations. The inciting agent is often difficult to pinpoint and may include food, environmental allergens in patients undergoing allergen immunotherapy, insect stings, and medications. Evidence of allergy by demonstration of a positive skin test to the inciting agent, is helpful only if skin testing is available. The only diagnostic modality that is useful in the diagnosis of anaphylaxis when IgE skin testing is not available and the inciting agent is unknown, is an elevated serum tryptase level. However, a diagnosis of anaphylaxis can be made without a tryptase level or if the tryptase level is normal. A simple, non-invasive test for patients with anaphylaxis is not currently available and would be helpful to diagnose and to guide further management options. Patients who develop anaphylaxis to environmental allergens or venoms during routine outpatient subcutaneous allergen or venom immunotherapy are an ideal population to study as we are able to evaluate these specific reactions in a controlled, clinical environment. Although anaphylaxis is uncommon, the incidence has been estimated to vary between 0.01 and 4 percent of all allergy injections. Subcutaneous allergen or venom immunotherapies are a well established form of therapy for patients with allergic rhinitis, allergic asthma, or a confirmed sensitivity to stinging insects. Serial blood sampling can be performed in this group of patients during a reaction and at baseline one week after a reaction, thereby allowing each patient to serve as his or her own biological control. Metabolomics is the study of metabolic pathways and the unique biochemical molecules which result from the regulatory response to physiological stressors, disease processes, drug therapy, or allergen or venom immunotherapy. By measuring changes in metabolite concentrations, the range of biochemical effects and therapeutic intervention can be determined. The investigator plans to use metabolic profiling of blood samples collected at the time of anaphylaxis and one week after, to see if a simple, non-invasive test for patients with anaphylaxis could be developed.