Health economics of allergen-specific immunotherapy in the United States.

Although 19 published studies report that allergen-specific immunotherapy (SIT) may decrease health care costs, a scant 4 pertain to the health economics of SIT in the United States (US). This editorial presents an overview of these published US studies and an appeal for additional US health economics research regarding SIT. We specifically focus on subcutaneously administered SIT (SCIT), the predominant and only US Food and Drug Administration–approved route of administration in the US. The first US health economics study of SCIT was published in 1999 (Table I). This was a 4-year (1988-1992) retrospective claims analysis of health maintenance organization enrollees with allergic rhinitis (AR). The study compared costs between patients who completed a course of SCIT (at least 61 injections over 3.5 years) and those who received less than a complete course during a mean 7-month follow-up period. Costs included all procedures associated with the administration and testing of SCIT and prescription medications, inpatient services, emergency department services, and outpatient services for the treatment of asthma, rhinitis, sinusitis, and nasal polyps. Average per-patient annual health care costs were higher for patients who completed SCIT than for those who did not ($508 vs $421; statistical significance not provided), with differences primarily attributable to medication costs. There are several limitations to this study. First, patients who completed SCIT had 30% higher costs for asthma and AR treatment in the year before SCIT initiation, which may reflect greater disease severity among SIT completers, and these pre-SCIT costs were not accounted for when examining cost differences after SCIT. Second, the follow-up period after SCIT completion may have been too brief to detect cost savings. Third, by virtue of their greater persistence to SCIT, completers also may have been more adherent