Background: The conventional schedule for subcutaneous immunotherapy with allergen extracts, although efficacious and safe, is slow during the dose-increase phase.
Objective: We sought to compare the efficacy and safety of subcutaneous immunotherapy with Dermatophagoides pteronyssinus standardized extract given in a 6-week cluster period and a conventional 12-week schedule during the incremental-dose phase.
Methods: Of 239 patients with rhinitis, allergic bronchial asthma, or both caused by D pteronyssinus , 120 were randomly assigned to the cluster schedule, and 119 were randomly assigned to the conventional schedule. A biologically standardized D pteronyssinus depot extract (ALK-Abelló S.A., Madrid, Spain) was administered in a placebo-controlled, double-blind fashion during the initial phase of cluster or conventional treatment. We recorded adverse reactions, clinical efficacy, cutaneous reactivity, and serum specific immunoglobulins to D pteronyssinus before immunotherapy, when the maximum dose was reached in the cluster and conventional schedules, and after 1 year of treatment.
Results: The cluster schedule reduced the time to maintenance dose by 46% and caused systemic adverse reactions (all mild) after only 0.15% of injections, with no differences in comparison with the conventional schedule. Cluster immunotherapy led to decreases in asthma and rhinitis symptoms, reduced the cutaneous reactivity, and produced the increase in specific IgE and IgG 4 levels on reaching the maintenance dose in the sixth week, 6 weeks earlier than with the conventional schedule.
Conclusion: The cluster schedule for the initial phase of immunotherapy with incremental doses of D pteronyssinus is a safe alternative to conventional immunotherapy and offers the further advantage of achieving clinical and immunologic improvements sooner.