Study design
The SysPharmPediA study is a multicenter European observational study with a case-control setting. The study design and study population were described previously in detail by Abdel-Aziz et al. 18Briefly, children aged 6-17 with doctor-diagnosed moderate-to-severe asthma were included at tertiary hospitals from four European countries: the Netherlands, Germany, Spain, and Slovenia. This study with registration identifier NCT04865575 (at www.clinicaltrials.gov) was carried out based on the Helsinki Declaration and approved by the medical ethics committee of the University Medical Center Utrecht, the Netherlands (NL55788.041.15); National Medical Ethics Committee, Slovenia (0120–569/2017/4), the ethics committee of University Regensburg, Germany (18–1034–101); Clinical Research Ethics Committee of the Basque Country, Spain (PI2015075); All participants or their caretaker or parents gave their informed consent.