International Study of Asthma and Allergies in Childhood (ISAAC) fase II: metodología y resultados de participación en España

Abstract

Background The ISAAC phase I results have supplied valuable information on the prevalence of asthma and allergy in childhood throughout the world. Objectives To describe the implementation and participation rate of normal children in each test performed in phase II of the ISAAC in the four Spanish cities participating the study, and to establish the influence of type of school and geographical situation (in a polluted or unpolluted area) in Cartagena. Methods The ISAAC phase II included a questionnaire on symptoms, risk factors and treatment, skin examination, skin-prick test, bronchial challenge test, total and specific IgE measurement, as well as mite and bacterial endotoxin determination in house dust. The questionnaire was distributed with a letter requesting authorization from the parents in primary schools (fourth and fifth grades) in sufficient number to achieve approximately 1,000 skin prick-test authorizations in each city. Results The participation rate for the questionnaire, skin examination, skin-prick test, blood extraction, bronchial challenge test, and dust collection was, respectively, for each city: Cartagena: 58.9, 49.2, 43.2, 33.1, 39.9 and 29.8 %; Almería: 42.5, 40.6, 39.1, 39.1 and 37.6 %; Valencia: 43.7, 30.4, 23.5, 21.5, 20.1 and 17.1%; Madrid: 53.2, 40.8, 38.6, 27.6, 30.6 and 21.1 %. In Cartagena, participation was significantly higher in private schools receiving a state subsidy and in those in unpolluted areas. Conclusions The participation rate was highly variable and lower than that among the European centres that have already completed the study. The rate was significantly influenced by geographical area and type of school.