Specific immunotherapy (SIT) in the treatment of allergic rhinitis.

Scientific background: Allergic rhinitis (AR) exhibits a prevalence of approx. 20% in Germany and causes enormous costs in the health care system. Specific immunotherapy (SIT) is considered to be the only potentially causal therapy for AR and mainly administered by two routes, subcutaneous (SCIT) and sublinguale (SLIT). SIT promises a reduction of symptoms and the need for medication in patients with AR.

Research questions: The question arises, to what extent is SIT effective and cost effective in the treatment of AR and which ethical-social and legal aspects have to be considered regarding its application.

Methods: The literature search was accomplished in the electronic data bases MEDLINE, EMBASE etc. in February 2008. The medical evaluation was based on systematic reviews of blinded, randomised controlled studies (RCT). The economic evaluation included health-economic studies on the basis of RCT. Additionally, it was also searched for publications explicitly addressing ethical-social and legal aspects of the use of SIT.

Results: MEDICAL EVALUATION: Two reviews on SCIT and three on SLIT were included in the medical evaluation. For the evaluation of SIT with grass pollen results for short and medium-term effects are considered from several studies, for SIT with other seasonal allergens (e. g. tree pollen) and with house dust mite allergens from clearly fewer studies and for SIT with other perennial allergens only from a few. The reviews report a significant reduction of the symptom and medication score in favour of SCIT with seasonal allergens and recognise the effectiveness at least for grass pollen allergens. Also for other seasonal allergens SCIT is appraised as effective. The reviews about SLIT determine a significant reduction of the symptom and the medication score in favour of SLIT vs. placebo in short and medium term follow-up in evaluations across all allergens. The subgroup analyses show a significant reduction of the symptom and medication score only in favour of SLIT with seasonal allergens. HEALTH ECONOMIC EVALUATION: Four publications about two health economic studies are identified, one of these publications on Alutard-SQ(®) injections (SCIT) and three on GRAZAX(®) tablets (SLIT). The studies provide more (on Alutard-SQ(®)) or less (on GRAZAX(®)) robust information, but no evidence on cost effectiveness of these SIT administration forms in patients with AR.

Discussion: The topic of the report is very broad, so that the evidence is summarised using systematic reviews. In particular the statistic heterogeneity of the studies found in the reviews considerably limits the strength of the findings. The included health economic studies show different methodical flaws, the largest potential bias is the projection of the magnitude of the medium-term clinical effects on the time period of nine years.

Conclusions: The effectiveness of SIT in patients with AR is not equally proven for all SIT administration forms and allergens. For SCIT and SLIT with grass pollen allergens short and medium-term effectiveness can be regarded as proven. These therapy forms should be used if the indication is appropriate and if no contraindications are present. Also SCIT and SLIT with other seasonal allergens such as tree pollen allergens can be an effective treatment option, but used with a certain restraint due to insufficient data especially in the case of SLIT. For SIT with house dust mite allergens and further perennial allergens no consistent proof of effectiveness are to be determined from the available information. Further research addressing non-grass pollen-associated SIT, allergen and manufacturer specific evaluations as well as asthma prevention is needed. Due to the lack of evidence the use of SIT can not be seen proven as cost effective. To provide such evidence further health economic studies with a long term follow-up are needed. The informed consent of the patients is an important ethical requirement within the use of SIT.