CFTR heterozygosity in severe asthma with recurrent airway infections: a retrospective review

RationalePatients with asthma who have neutrophilic bronchitis may have an underlying cause leading to increased susceptibility to airway infections.MethodsRetrospective review of patients with asthma who had a previous history of recurrent exacerbations that had been associated with airway or sinus infections referred to a tertiary asthma center between 2005 and 2020. Demographics, clinical features, and airway inflammation type determined by sputum cytometry were compared between CFTR carriers and non-carriers. Multiple linear regression was used to identify clinical predictors of CFTR carrier status. Response to nebulized hypertonic saline was assessed by comparing the number of infective exacerbations before and after its initiation.Results75 patients underwent CFTR mutation testing. Of these, 13 (17%) were CFTR carriers. The most common mutation was Δ$$\Delta$$F508. CFTR carriers were older (adjusted odds ratio 1.06 (CI 95% 1.01, 1.13)) and had more frequent flares requiring hospitalization (4.19 (1.34, 24.74)). Neutrophilic airway inflammation was the most common inflammatory subtype in CFTR carriers, though 8/13 also had eosinophilic bronchitis. Nebulized hypertonic saline was well tolerated by most and reduced the frequency of infective exacerbations.ConclusionsThe prevalence of CFTR heterozygosity in this cohort with recurrent neutrophilic bronchitis is higher than in the general population. Respiratory disease in CFTR carriers is associated with older age and may cause significant morbidity. Airway neutrophilia is the most common inflammatory subtype, but > 50% had eosinophilic bronchitis requiring treatment. Hypertonic saline appears to be well tolerated and effective in reducing the number of infective exacerbations.