How well does spirometry capture the symptom range in primary ciliary dyskinesia? – a cross-sectional national study
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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.
