Introduction Patients with primary ciliary dyskinesia (PCD) present a variety of respiratory symptoms. Spirometry, particularly forced expiratory volume in 1 s (FEV1), is the most commonly used outcome measure in clinical follow-up, however, it is not known how well it captures the range of respiratory symptoms experienced by patients.

Methods We sent the FOLLOW-PCD questionnaire to all patients ≥14 years and parents of children, registered in the Swiss PCD Registry, asking about upper and lower respiratory symptoms. In patients who had a routine lung function done within a year of survey completion, we extracted data from clinical records and calculated spirometric indices z-scores based on the Global Lung Function Initiative references. We used linear regression to study associations between FEV1, forced vital capacity (FVC), FEV1/FVC and frequency of respiratory symptoms, adjusted for age, sex, and regular physiotherapy.

Results 64 out of 99 invited patients (67%) completed the survey; for 54 of them (median age 24 years, IQR 15-47; 50% females) we also had an FEV1 measurement (mean z-score - 2.29 [- 3.37 – −1.03]), with 2.2 months median time between survey and lung function test. Patients reporting wheeze (76%) had lower FEV1 and FEV1/FVC z-scores (FEV1 z-score for infrequent and frequent wheeze compared to no wheeze: −1.13 [95%CI −2.13 – −0.12] and −1.11 [−2.20 – - 0.20] respectively). Similarly patients reporting frequent shortness of breath (29.5%) had also lower FEV1 and FEV1/FVC z-scores (FEV1 z-score for frequent shortness of breath compared to no shortness of breath: −1.27 [−2.50 – −0.04]). We found no signs of association between reported nasal symptoms, snoring, cough, sputum production, and chest pain with FEV1, FVC or FEV1/FVC.

Conclusion In our study, self-reported wheeze and frequent shortness of breath were associated with lower FEV1 and FEV1/FVC, commonly used for patient follow-up. However, we need additional outcome measures e.g., lung clearance index, imaging outcomes, or upper airway assessments, together with regular and standardised assessment of patient-reported symptoms, to capture the range of respiratory morbidity patients with PCD experience in daily life and guide management successfully.

The authors have declared no competing interest.

This study was supported by a Swiss National Science Foundation Ambizione fellowship (PZ00P3_185923) and a project grant (SNSF_10001934). PCD research at ISPM Bern also receives funding by the Swiss Lung Association. The authors participate in the BEAT-PCD clinical research collaboration, supported by the European Respiratory Society, and they are supporting members of the ERN-LUNG (PCD core).

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

Institute of Social and Preventive Medicine, University of Bern, Bern, Switzerland. Ethical approval from the Cantonal Ethics Committee of the Canton of Bern in 2015 (KEK-BE: 060/2015).

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I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

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I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

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CH-PCD study data is not deposited at an open access repository. Because of the rarity of the disease although data is pseudonymised, it may include still sensitive information; therefore, participants were not asked to give consent to have their data deposited publicly. Partial datasets for specific analyses including individual patient data and a data dictionary defining each included field can be available from Dr Goutaki (myrofora.goutakiunibe.ch) upon reasonable request.