Questionnaires
Parents filled out an initial questionnaire about medical history, living environment, and quality of life. In the period between the first and final visit (± six weeks), parents kept a questionnaire based journal about their child’s symptoms. The most clinically relevant parameters extracted from these questionnaires were age at onset of noisy breathing, age at first cold, number of colds, parent reported outcome about burden in the past three days (PROb) and parent reported outcome about symptoms in the past three days (PROs).