Long-lasting effects of sublingual immunotherapy for house dust mites in allergic rhinitis with bronchial hyperreactivity: A long-term (13-year) retrospective study in real life.

Background: Subcutaneous immunotherapy for respiratory allergy has shown a long lasting efficacy after its discontinuation, whereas evidence in the case of sublingual immunotherapy (SLIT) is weak. This retrospective study evaluates whether SLIT exerts a long-lasting effect and whether it relates to its duration.

Methods: Sixty-five patients allergic to mite and positive to methacholine challenge 13 years ago were studied. Twelve (control group, SLIT 0) were treated for 4 years only with standard pharmacological therapy (SPT), while 53 received SLIT and SPT. Among these, four groups were identified according to SLIT duration. Fifteen patients were treated for 1 year (SLIT 1), 10 for 2 (SLIT 2), 14 for 3 (SLIT 3) and 14 for 4 years (SLIT 4). Clinical parameters (symptom monthly score, SMS), bronchial reactivity and FEV1 were evaluated in 1992 (run-in), 1993 (baseline) and every 2 years from 1997 to 2005.

Results: Two to 3 years after the treatment ended, a positive effect on SMS, but not methacholine challenge and FEV1, was seen in the SLIT groups versus SLIT 0. At this time interval an effect on methacholine challenge was also seen in SLIT 3. After 7-8 years a significant difference was seen for SMS, i.e., it was significantly better in SLIT 4 than in the other groups, while bronchial reactivity was still improved in SLIT 1, 3 and 4 only after 5-6 years.

Conclusions: The effects of a 4-year SLIT on clinical parameters but not bronchial reactivity and FEV1 last 7-8 years after its discontinuation. SLIT shorter than 4 years yields proportionally less impressive results.