Systemic reactions with aeroallergen cluster immunotherapy in a clinical practice.

Background: Subcutaneous allergen-specific immunotherapy is a proven, highly effective treatment for immunoglobulin E-mediated diseases. Despite its proven benefits, only a small percentage of patients with allergic disease use immunotherapy, in part because of the inconvenience associated with treatment. Cluster allergen immunotherapy may offer patients a more convenient treatment option but is prescribed infrequently because of the perception that accelerated immunotherapy buildup leads a higher rate of systemic reactions.

Objective: To examine the safety of cluster immunotherapy and identify risk factors for systemic reactions during cluster buildup.

Methods: A retrospective, observational review in a large, multicenter allergy practice group was conducted for patients receiving cluster immunotherapy between May 2008 and October 2010.

Results: Data from 441 patients receiving cluster immunotherapy were collected. Forty-eight patients (10.9%) experienced systemic reactions. Based on the World Allergy Organization Subcutaneous Immunotherapy Systemic Reaction Grading System, 18 grade 1 reactions (38.3%), 23 grade 2 reactions (48.9%), 5 grade 3 reactions (10.6%), 1 grade 4 reaction (2.1%), and no grade 5 reactions were seen. Risk factors for a systemic reaction included: female sex, physician diagnosis of asthma, age 21 to 40 years, and inclusion of certain allergens in the immunotherapy vaccine.

Conclusions: Cluster immunotherapy allows patients to reach their immunotherapy maintenance dose more rapidly and may lead to more rapid symptomatic improvement. However, the cluster buildup may lead to a higher rate of systemic reactions. Identifying risk factors for systemic reactions will help improve the safety of cluster immunotherapy.