Idiopathic Chronic Productive Cough and Response to Open-label Macrolide Therapy: An Observational Study

Background And Objective: Adult patients with chronic productive cough of unknown cause are commonly seen in respiratory clinics. We have previously described a subgroup of these patients who have a short-lived response to standard antibiotic treatment but a prolonged response to 3 months of low-dose azithromycin therapy.

Methods: This observational study describes the physiological, radiological and pathological features of this patient cohort along with their response to a 12-week open-label trial of 250 mg azithromycin thrice weekly.

Results: A total of 30 subjects with a mean age of 57 were recruited. The majority demonstrated airway dilatation on high-resolution computed tomography (HRCT) scan without evidence of established bronchiectasis (n = 21) and non-specific chronic inflammatory changes on bronchial biopsy (n = 15/17). Twenty-nine subjects completed 3 months of azithromycin with a significant improvement in median Leicester Cough Questionnaire (LCQ) score (-6.3 points, P < 0.00001), reduction in median 24-h sputum volume (-5.8 mL, P = 0.0003) and improvement in sputum colour (P = 0.003). Patients responsive to azithromycin (n = 22) demonstrated neutrophilic or paucigranulocytic airway inflammation, whereas five subjects with eosinophilic airways inflammation did not respond symptomatically to azithromycin.

Conclusion: We describe a cohort of patients with chronic productive cough not adequately described by existing disease labels whose symptoms responded well to low-dose azithromycin. Many of the features are similar to the paediatric condition protracted bacterial bronchitis.