Background: Asymptomatic aeroallergen sensitisation affects approximately 10% of Western adolescents and is an established risk factor for the development of respiratory allergy. The reported incidence is 2-20% annually. Previous studies are based on out-seasonal symptom recollection or selected populations, conferring bias towards higher incidence rates.
Objective: The aim was to determine the incidence of onset of symptoms among clinically well-characterised asymptomatic, sensitised subjects compared with controls, and to evaluate the predictive values of common allergological tests.
Methods: We performed a prospective, clinical, non-interventional, 2-year follow-up study on subjects (identified by population screening) with seasonal allergic birch or grass pollen rhinitis (n = 52), asymptomatic sensitisation to grass or birch (AS, n = 52) or non-atopic, healthy control subjects (n = 39). Experimental allergen susceptibility was assessed at inclusion and at follow-up by skin prick test, conjunctival challenge, intradermal late-phase reaction and measurement of specific IgE. Participants completed in-seasonal symptom and medication diaries during 2 subsequent seasons.
Results: We observed an annual incidence rate of 5% for the onset of symptoms in the AS group (healthy control group 0%). At baseline, the AS group displayed intermediate experimental allergen susceptibility. Subjects developing symptoms had higher levels of specific IgE and larger late-phase reaction than those persistently asymptomatic. However, the positive predictive values were low (14-27%) in contrast to the negative predictive values (95-100%).
Conclusion: In a well-characterised young population, asymptomatic aeroallergen sensitisation conferred a low risk for onset of symptoms during the 2-year follow-up. Persistent asymptomatic phenotype could be accurately predicted by negative results from simple allergological testing.
Copyright © 2011 S. Karger AG, Basel.