Swiss Paediatric Airway Cohort

Background: Many studies have investigated the epidemiology of asthma in childhood, but most were based on data from the general population gathered either in cross-sectional or longitudinal surveys in schoolchildren. Objectives: The Swiss Paediatric Airway Cohort (SPAC) was set up in 2017 as a large, longitudinal database that is representative of children and adolescents visiting physicians in Switzerland for recurrent wheeze, cough, and exercise- or sleep-related respiratory symptoms. It will constitute a national research platform for studying healthcare provision, phenotypes and prognosis of these problems, and a sampling frame for conducting nested studies. Methods: Recruitment and participation: The SPAC study recruits patients aged 0-16 that are referred to a paediatric outpatient clinic for recurrent respiratory symptoms. Families receive a SPAC information package containing an invitation letter, study information leaflet, informed consent form, and questionnaire. Physicians introduce the study to them, answer questions, and collect informed consent forms. Completed questionnaires are brought by families to the clinics or sent directly by families to the SPAC study centre using a prepaid return envelope. Eligible patients have consultations in participating clinics regardless of their study participation. No tests are performed specifically for SPAC; examinations and tests are done only if clinically indicated or ordered by the referring physician. Examinations such as lung function, allergy, blood, or bronchial challenge tests are done using respective standard procedures in the clinics. SPAC research team members visit participating centres at regular intervals to collect data. During the first year, caregivers or patients who are 14 years or older receive short online questionnaire through a link via email. One year after enrolment and each year thereafter, caregivers receive a follow-up questionnaire by post. Information collected: Questionnaires: At baseline families complete a detailed questionnaire that includes sections on frequency, duration, severity, triggers, and history of upper and lower respiratory symptoms, and diagnoses, treatments, health behaviours, environmental factors, family history, and contact information. The monthly online questionnaires focus on symptoms, infections, and treatments which may change short-term. The yearly follow-up questionnaires focus on symptoms, treatments, and important risk factors during the past 12 months. Postal addresses for mailing are obtained from hospital records and updated by contacting community registration offices, a procedure used successfully for other registries and cohort studies in Switzerland. Questionnaires are currently available in German and French. Medical records: Information obtained from medical records includes reasons for referral; anthropometric measures; results from the physical examination and diagnostic tests including pulmonary function, allergy, and blood tests; information about asthma control; and final diagnoses and prescribed treatments. Linkage to routine data: For specific analyses, probabilistic record linkage will be used to merge data from SPAC with routine datasets collected by the Swiss Federal Statistical Office. Study database: The SPAC database is web-based, using the Research Electronic Data Capture (REDCap) platform developed at Vanderbilt University. REDCap is widely used in academic research and allows data entry and extraction in various formats. Current status of the project: SPAC recruits participants from 10 clinics in Switzerland including the children's hospital in Aarau, the University Children's hospital in Basel, the University Children's Hospital in Bern, the Children's hospital in Chur, a private paediatric pulmonology clinic in Horgen, the University Children's hospital in Lausanne, the Children's hospital in Luzern, the Children's hospital in St. Gallen, a private paediatric pulmonology clinic in Worb, and the University Children's Hospital in Zurich. By October 2023, 4344 children have agreed to participate in SPAC. Publications and plain language summaries are listed on the study website: https://www.spac-study.ch/publikationen/ Funding: Setting up SPAC was funded by the Swiss National Science Foundation (SNF32003B\_162820, SNF320030\_182628, SNF320030\_212519), and several local funding bodies including the Swiss Lung Association, the Lung League of St. Gallen, and the Allergiestiftung Ulrich Müller-Gierok.