Safety of House Dust Mite Subcutaneous Immunotherapy with a rush and cluster combination protocol in the build-up phase

Conventional and cluster subcutaneous immunotherapy (SCIT) are effective but may be time-consuming. Rush SCIT may offer a more convenient treatment option to patients and be of shorter duration; however, it is also associated with a higher incidence of systemic adverse reactions. Therefore, a combination of protocols between rush and cluster SCIT could have a superior risk-benefit ratio.To determine the safety of the combination of rush and cluster HDM-SCIT and to identify the risk factors for local and systemic adverse reactions.We retrospectively reviewed the charts of patients who received HDM-SCIT, with rush and cluster combination protocols, at a tertiary care hospital between January 2009 and December 2020. Data were collected at the initial visit (demographic data; underlying allergic disease; current medication; and laboratory investigation results including skin prick test, serum specific IgE (sIgE) levels to aeroallergen, total IgE, and eosinophil count) and follow-up visits (rate and severity of local and systemic adverse reactions).In total, 698 injections (28 patients) were reviewed. Overall, 13 patients developed systemic adverse reactions, at 3% (21/698) per injection visit. All reactions occurred within 60 minutes. In total, 6 patients experienced large local reactions, at 1.1% (8/698) per injection visit. A high level of sIgE to D. pteronyssinus was significantly associated with systemic adverse reactions (HR = 1.02; P = 0.009).HDM-SCIT with a combination of rush and cluster schedules in the build-up phase could be used as an alternative protocol, given its acceptable systemic adverse reaction rate and shortened duration.