Five-Year Follow-up on the PAT Study: Specific Immunotherapy and Long-term Prevention of Asthma in Children
Authors: Kaplan Michael R. , Mikita Cecilia P. 
Published: November 2007

Niggemann B, Jacobsen L, Dreborg S, et al. Allergy. 2006;61:855–859
PURPOSE OF THE STUDY. The Preventive Allergy Treatment (PAT) study was designed to investigate the preventive effect of specific immunotherapy (SIT) on the development of asthma in children suffering from allergic rhinitis. SIT was performed as a 3-year course of subcutaneous immunotherapy with extracts of grass and/or birch pollen. The PAT study showed that SIT can prevent the development of asthma in children suffering from seasonal allergic rhinoconjunctivitis. This article was a follow-up evaluation on the development of asthma in these children 2 years after discontinuation of SIT versus no treatment.
STUDY POPULATION. Children aged 6 to 14 with rhinoconjunctivitis triggered by allergy to grass and/or birch pollen were enrolled onto the PAT study. A total of 183 of the 205 children (now aged 11–20 years) from the PAT study were included in this 5-year follow-up evaluation.
METHODS. Of the initially randomly assigned 205 patients, there were 183 patients (95 receiving SIT, 88 controls) suffering from rhinoconjunctivitis caused by allergy to grass and/or birch who underwent conjunctival provocation testing, methacholine bronchial provocation testing, evaluation for asthma, and recording of rhinitis and conjunctivitis visual analog scores. Asthma was defined as recurrence of at least 2 of the 3 following symptoms within the last 12 months that were not only triggered by infection and responded to treatment with β agonists: cough, wheeze, and shortness of breath.
RESULTS. Of the 183 patients evaluated after 5 years, 142 had no asthma at inclusion, and 8 children dropped out of the study. Patients without asthma before the start of SIT (n = 142) were analyzed for the development of asthma, which was the primary end point of this study, after the 5-year period. Of the 75 patients who received SIT, 15 developed asthma, whereas 29 of the 76 control patients developed asthma (P &lt; .01). On the basis of the visual analog scores of conjunctivitis and rhinitis, the SIT-treated group had a significant improvement from baseline to 5 years compared with the controls (P &lt; .001). The conjunctival sensitivity measured by provocation tests were significantly reduced in the active group compared with the control group (P &lt; .001).
CONCLUSIONS. This study showed that the benefits of SIT (ie, the reduction of symptoms and prevention of asthma) persisted 2 years after termination of treatment of children with allergic rhinoconjunctivitis caused by grass and/or birch.
REVIEWER COMMENTS. Although the results that allergen immunotherapy may reduce the symptoms of allergic disease and the onset of asthma are encouraging, the manner in which asthma was defined in this study, based primarily on subjective findings, limited the significance of the results. Furthermore, in the United States, we generally perform SIT with more than just timothy grass (Phleum pratense) and birch pollen (Betula verrucosa) because of multiple aeroallergen sensitization; therefore, it is difficult to generalize the findings of this study to our typical patient population.