Background: Consistent use of reliable and clinically appropriate outcome measures is a priority for clinical trials, with clear definitions to allow comparability. We aimed to develop a core outcome set (COS) for pulmonary disease interventions in primary ciliary dyskinesia (PCD).

Methods: A multidisciplinary international PCD expert panel was set up. A list of outcomes was created based on published literature. Using a modified 3-round e-Delphi technique, the panel was asked to decide on relevant endpoints related to pulmonary disease interventions and how they should be reported. First, inclusion of an outcome in the COS was determined. Second, the minimum information that should be reported per outcome. The third round finalized statements. Consensus was defined as ? 80% agreement among experts.

Results: During the first round, experts reached consensus on 4 out of 24 outcomes to be included in the COS. Five additional outcomes were discussed in subsequent rounds for their use in different sub-settings. Consensus on standardised methods of reporting for the COS was reached. Spirometry, health-related quality of life scores, microbiology and exacerbations were included in the final COS.

Conclusion: This expert consensus resulted in a COS for clinical trials on pulmonary health among people with primary ciliary dyskinesia.