Primary Ciliary Dyskinesia in Adult Bronchiectasis

Bronchiectasis is a chronic respiratory disease characterized by irreversible bronchial dilatation, impaired mucociliary clearance, and recurrent infection. Despite comprehensive evaluation, 40-80% of adults with non-cystic fibrosis (CF) bronchiectasis have no identifiable cause. This diagnostic absence limits opportunities for targeted therapy, individualized prognostication, and potential genetic counseling.

Primary ciliary dyskinesia (PCD) is an inherited disorder of motile cilia that leads to chronic otosinopulmonary disease. Nearly 100% of affected individuals develop bronchiectasis by adulthood (4). Diagnosis is complex with no 'gold standard' test and requires multiple specialized diagnostics-most available only at large referral centers. In current North American practice, evaluation of suspected PCD frequently begins with measurement of nasal nitric oxide (nNO), an accurate screening tool when performed correctly. However, testing errors occur due to discrepancies in technique, and false negatives are well-described in a growing list of PCD genotypes harboring preserved ciliary ultrastructure, as well as in select primary immunodeficiencies.

High-speed video microscopy analysis (HSVA) is a key PCD diagnostic tool that directly visualizes ciliary beating ex vivo, providing detailed assessment of ciliary beat frequency, waveform, and pattern. As a functional assay, HSVA has substantial diagnostic value in cases where PCD would otherwise remain unrecognized (e.g., patients with normal nNO, normal/nondiagnostic transmission electron microscopy (TEM), or incomplete genetic testing). When performed using standardized protocols and blinded review, multicenter studies demonstrate excellent diagnostic performance, with sensitivities and specificities of of 96-100% and 91-96% respectively. Air-liquid interface (ALI) culture further refines accuracy by differentiating inherent ciliary defects from secondary, inflammation-induced abnormalities.

Growing evidence suggests that PCD remains significantly underrecognized worldwide. Large-scale genomic analyses now estimate a global prevalence as high as 1 in 7,500-two to four times higher than previous estimates. These findings are amplified in adults with bronchiectasis: a recent genomic sequencing study of patients with idiopathic bronchiectasis revealed that more than 10% carried pathogenic variants in motile ciliopathy genes, yet the vast majority had never undergone targeted testing for PCD.

Collectively, these data indicate that a substantial proportion of adults with bronchiectasis may have undiagnosed PCD. Identifying this population has meaningful clinical implications. Confirmation of PCD enables precise airway clearance and infection-control strategies, recognition and treatment of potential cardiac and multi-organ manifestations, and appropriate genetic counseling. Moreover, as disease-modifying and gene-targeted therapies advance toward clinical use, timely and accurate diagnosis will be essential to ensuring equitable access to emerging treatments.

Hypothesis: Unrecognized PCD is prevalent within a significant and measurable proportion of adults with non-CF bronchiectasis. The combined use of upfront nNO and HSVA of ALI-cultured ciliated nasal epithelia represents a unique, highly sensitive, and potentially diagnostic method to help identify this patient population.