Background: Some aspects of sublingual immunotherapy (SLIT) still need to be addressed: magnitude of the clinical efficacy, effect on the bronchial hyperreactivity adherence to treatment, preventive effect. We attempted to clarify these points in a randomized open, controlled, two parallel group study in a real-life setting.
Methods: Five hundred and eleven patients with allergic rhinitis with or without intermittent asthma were randomized to drugs only or drugs + SLIT (rate 2 : 3) for 3 years. The clinical score (symptoms + drug intake) was measured each year during the allergen exposure. Pulmonary function test, methacholine challenge and skin tests were performed at the beginning and at the end of the study. Adherence to treatment was assessed by measuring the consumed extract.
Results: Three hundred and nineteen patients received SLIT and 192 drugs only. Dropouts were 15% in the SLIT group and 12% in the controls. There was a significant improvement of clinical scores in the SLIT group: baseline 147 ± 3.3, first year 72.9 ± 1.3, second year 68.3 ± 1.8, third year 54.7 ± 2.8 (P < 0.0001 vs baseline). Control group: baseline 138 ± 2.3, first year 124.1 ± 3.7, second year 111 ± 3.3, third year 121 ± 3.8 (P = NS). Only four patients reported systemic itching. Adherence was >80% in 72% and >60% in 18% of patients. The number of patients with a positive MCh challenge decreased significantly after 3 years only in the SLIT group. New skin sensitizations appeared in 38% of the controls and in 5.9% of the SLIT patients (P = 0.01).
Conclusion: Sublingual immunotherapy approximately halved the clinical scores and significantly reduced the bronchial hyperreactivity. Similarly to subcutaneous immunotherapy, SLIT displayed a preventive effect on the onset of new skin sensitizations. The adherence rate was quantitatively satisfactory.