BACKGROUND: One fourth of the adult population in Europe suffer from respiratory allergy. Subcutaneous-allergen-specific-immunotherapy (SCIT) has long-term disease modifying effect on disease specific Health-Related Quality of Life (HRQoL). The purpose of this study was to assess the effect of SCIT on alternative disease outcomes in patients with grass-pollen and/or house dust mite induced allergic rhino-conjunctivitis and/or an asthma diagnosis. Focus was on expressing outcomes in terms of generic quality of life (Quality-Adjusted-Life-Years (QALY)) and reductions in sick days.
METHODS: The study was a multi-centre study with prospective follow-up. 248 patients were initiated on SCIT. The disease specific Rhino-conjunctivitis Quality of Life Questionnaire (RQLQ) and two generic (HRQoL) instruments 15D and EQ-5D were used at baseline and at follow-up. The outcome measures included change in; disease severity, RQLQ-scores, number of days with symptoms- and number of sick days per year and finally changes in generic HRQoL and thus, QALY. Disease severity was assessed by specialist doctors; severity of rhino-conjunctivitis was classified according to the Allergic Rhinitis and its Impact on Asthma (ARIA) and asthma severity according to the Global Initiative for Asthma (GINA guideline). The remaining outcome measures were assessed by the patients in questionnaires at baseline and at follow-up. An intension to treat approach was applied. For missing items imputation of sample mean base-line values or follow-up values were used after specified criteria. The effect of SCIT on rhino-conjunctivitis and/or asthma diagnoses was analysed at follow-up using three logistic regression models.
RESULTS: The disease severity showed significantly improved disease control. Mean RQLQ-score was reduced from 3.02 at baseline to 2.00 at follow-up. Average annual days with symptoms were reduced from 189 to 145 days whilst annual sick days were reduced from 3.7 to 1.2 days. The 15D-score increased from 0.83 to 0.86 and the EQ-5D-score from 0.70 to 0.77, which indicated an annual gain per patient of 0.03-0.06 QALY.
CONCLUSIONS: Allergic patients suffering from rhino-conjunctivitis alone or rhino-conjunctivitis and asthma experience significantly increased HRQoL and they gain 0.03-0.06 QALY, when treated with SCIT for one year.
TRIAL REGISTRATION: The study was registered at ClinicalTrials.gov with the identifier: NCT01486498.