A single centre retrospective study of systemic reactions to subcutaneous immunotherapy

Abstract

Background Subcutaneous immunotherapy (SCIT) is the standard approach for treating patients with sensitizations to aeroallergens. However, immunotherapy can trigger severe systemic reactions if delivered inappropriately or to high risk patients. We sought to characterize and quantify SCIT systemic reactions requiring epinephrine administration during a 6-year period in a Canadian setting following the recommendations for components and dosages published in the 2010 Canadian Society of Allergy and Clinical Immunology (CSACI) Immunotherapy Manual. Methods A single centre retrospective chart review was performed for all patients with systemic reactions to subcutaneous immunotherapy requiring intramuscular epinephrine injection between January 2011 and October 2017. Each systemic reaction requiring epinephrine was reviewed for baseline patient characteristics, details of the reaction, and reaction severity. Research ethics approval was obtained through McMaster University. Results 28 of 380 patients experienced a systemic reaction requiring epinephrine administration, with an incidence rate of 1 per 1,047 injection visits (0.095%). 26 of the 28 reactions occurred within the mandatory 30-minute observation period post allergen immunotherapy. Of the 28 patients that experienced a systemic reaction to SCIT, 11 patients had asthma and 5 patients had a history of possible food allergy. All of the systemic reactions occurred during injections from vial number 4, and five patients reacted to their first shot of a re-ordered extract. 10 of the 28 patients required more than one intramuscular injection of epinephrine, and 20 of 28 patients were transferred to the hospital by ambulance. Conclusions This is the first Canadian study to review patients with systemic reactions to subcutaneous immunotherapy. Several best practice methods were employed throughout the study to optimize subcutaneous delivery of immunotherapy extract, and our recorded per injection incidence rate for systemic reactions was comparable or below the rate published in similar studies. The recommendations in the CSACI Immunotherapy Manual provide an approach to standardizing prescriptions for SCIT to maximize immunotherapy efficacy and reduce the risk of systemic reactions, though similar studies in larger multicenter settings are needed to confirm these observations. These observations provide important objective information to clinicians about the potential risks for systemic reactions in patients considering SCIT.

Comparing the risk of anaphylaxis requiring epinephrine in oral immunotherapy and subcutaneous immunotherapy: A review of recent Canadian real-world literature

“…Of the patients who experienced systemic reactions, 26 of 28 (92.9%) received epinephrine during their clinic visit, whereas 2 of 28 reactions (7.1%) occurred outside the 30-minute mandatory observation period, with administration of epinephrine occurring outside the clinic setting. 5 This is comparable to a review of 860 patients receiving either aeroallergen or venom SCIT from a single academic allergy and immunology center with multiple allergists over a 12-month period in 2019, which showed the incidence of systemic reactions requiring epinephrine was 10 in 4242 injections or 0.24% (all of these reactions resulted from aeroallergen SCIT). 6 The per capita incidence of epinephrine use for this study is unavailable.…”

“…A single-center retrospective review of 380 patients from a community allergy and immunology clinic between 2011 and 2017 showed that the incidences of systemic reaction requiring epinephrine were 28 in 380 patients (7.4%) and 1 in 1047 injection visits (0.095%). 5 No number of patients who had dropped out or discontinued SCIT secondary to side effects during the study time frame was reported. Of the patients who experienced systemic reactions, 26 of 28 (92.9%) received epinephrine during their clinic visit, whereas 2 of 28 reactions (7.1%) occurred outside the 30-minute mandatory observation period, with administration of epinephrine occurring outside the clinic setting.…”

“…The rate of systemic reactions is low, and several randomized controlled studies, meta-analyses, and recent case series support the safety of SCIT. 2 , 3 , 4 , 5 , 6 The combination of safety and efficacy has resulted in SCIT becoming a common treatment modality offered in both academic and community allergy practices. Like SCIT, oral immunotherapy (OIT) is an allergen-specific approach, but it involves introduction of an allergenic food into the diet in increasing doses.…”

Adverse events in children and adolescents undergoing allergen immunotherapy for respiratory allergies—Report from the Allergen Immunotherapy Adverse Events Registry (ADER), a European Academy of Allergy and Clinical Immunology taskforce

“…AEs were recorded in overall about 10% of patients. The range of local and systemic reactions reported from previous studies is as low as 1.5% 23 up to 17.9% 25–28 . This is not surprising, taking into account that patient selection, type of product, adjuvant and route of administration as well as intensity of follow‐up may affect safety outcomes and vary considerably.…”

“…The range of local and systemic reactions reported from previous studies is as low as 1.5% 23 up to 17.9%. [25][26][27][28] This is not surprising, taking into account that patient selection, type of product, adjuvant and route of administration as well as intensity of follow-up may affect safety outcomes and vary considerably. ADER is a multicenter registry that includes patients from 8 countries with different characteristics, a wide spectrum of AIT products and administration protocols.…”