High total airway mucin concentrations may serve as a diagnostic biomarker of chronic bronchitis, thus paving the way for the development of therapeutic targets for the disorder. The investigators of the current analysis, published in the New England Journal of Medicine, hypothesized that high total mucin concentrations produce the sputum and disease progression that are distinguishing features of chronic bronchitis.
Patients with chronic obstructive pulmonary disease (COPD) typically present with chronic bronchitis and emphysema components. The COPD status of 917 participants from the Subpopulations and Intermediate Outcome Measures in COPD Study (SPIROMICS) was assessed using questionnaires, chest computed tomography scans, spirometry, and sputum examination. Total mucin concentrations in sputum were measured as well.
The respiratory secreted mucins MUC5AC and MUC5B were measured in a subgroup of 148 patients. The sensitivity and specificity of total airway mucin concentrations in sputum as a biomarker for chronic bronchitis were also examined in an independent cohort (n=94) who had never smoked and current or former smokers with or without chronic bronchitis.
The mean total mucin concentrations were higher in current or former smokers with severe COPD vs nonsmoker controls (3166 μg/mL vs 1515 μg/mL, respectively). Mucin concentrations were also higher in participants with ≥2 respiratory exacerbations per year vs those with no exacerbations (4194 μg/mL vs 2458 μg/mL, respectively). Absolute concentrations of MUC5B and MUC5AC in current or former smokers with severe COPD were approximately 3 times as high and 10 times as high, respectively, compared with patients who had never smoked.
The researchers concluded that airway mucin concentrations may quantify a key component of the pathophysiologic cascade of chronic bronchitis that produces sputum and mediates disease severity.
Kesimer M, Ford AA, Ceppe A, et al. Airway mucin concentration as a marker of chronic bronchitis. N Engl J Med. 2017;377(10):911-922.