Competing interests

The authors declare no competing interests.

Conflict of interest

No conflict of interest reported by FD, EV, SV and CS. FS has received grants or contracts from AstraZeneca, GlaxoSmithKline, Chiesi, Novartis, TEVA, Sanofi and ALK; has received consulting fees from AstraZeneca, Chiesi and GlaxoSmithKline; has received payment or honoraria for lectures, presentations, speakers' bureaus, manuscript writing or educational events from AstraZeneca, GlaxoSmithKline, Chiesi, ALK, Novartis and TEVA and has received support for attending meetings and/or travel from AstraZeneca, Chiesi and Sanofi. RL has received grants or contracts from Sanofi, AstraZeneca and GlaxoSmithKline and has received lecture or consultancy fees from Sanofi, GlaxoSmithKline, AstraZeneca, Novartis and Chiesi. GB has received payment or honoraria for lectures, presentations, speakers' bureaus, manuscript writing or educational events from AstraZeneca, Sanofi Regeneron, Boehringer Ingelheim, Chiesi, Novartis and MSD and he is the current president of the Belgian Respiratory Society. AM has received support for research from AstraZeneca, GlaxoSmithKline and Chiesi; has received payment or honoraria for lectures, presentations, speakers' bureaus, manuscript writing or educational events for AstraZeneca, GlaxoSmithKline and Chiesi; has received support for attending meetings and/or travel from AstraZeneca (ATS 2022), Chiesi (ATS 2023 and CHEST 2023) and Sanofi (ERS 2022 and ERS 2023) and has participated on an Advisory Board for AstraZeneca and GlaxoSmithKline. RP has received consulting fees from AstraZeneca, Chiesi, GlaxoSmithKline, MSD and Sanofi and has received payment or honoraria for lectures, presentations, speakers' bureaus, manuscript writing or educational events from AstraZeneca, Chiesi and GlaxoSmithKline. CP has received grants or contracts from AstraZeneca, Chiesi and GlaxoSmithKline; has received consulting fees from ALK-Abello, AstraZeneca, Chiesi, GlaxoSmithKline, Sanofi and Stallergènes and has received payment or honoraria for lectures, presentations, speakers' bureaus, manuscript writing or educational events from ALK-Abello, AstraZeneca, Chiesi, GlaxoSmithKline, Sanofi and Stallergènes. SH has received consulting fees from AstraZeneca, GlaxoSmithKline, MSD and Sanofi; has received scientific grants from Chiesi; has received support for attending meetings from AstraZeneca, GlaxoSmithKline and Sanofi and is the current president of the working group Asthma of the Belgian Respiratory Society.

Ethical Approval

This retrospective study involving human participants was conducted in accordance with the ethical standards of the institutional and national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. The Ethical Committee (IRB) of UZ Brussel approved this study. Ethical approval for the BSAR database was obtained through the Ethical Committee of UZ Gent (Central ethics committee UZ Gent B67020084584).

Consent to Participate

Informed consent was obtained from all individual study participants at the time of first enrollment in the BSAR (Central ethics committee UZ Gent B67020084584).

Consent to publish

Patients gave informed consent for publication at the time of first enrollment in the BSAR (Central ethics committee UZ Gent B67020084584).