New Lung Mucin Score Improves Identification of Chronic Bronchitis: Study
USA: A new study published in NEJM Evidence reports that a novel sputum-based scoring system may improve the identification of chronic bronchitis by providing a more objective and biologically grounded assessment of airway mucus abnormalities. The approach moves beyond symptom-based diagnosis and may help refine risk assessment and disease monitoring in patients with muco-obstructive lung diseases.
The study was led by Mehmet Kesimer of the Marsico Lung Institute/Cystic Fibrosis and Pulmonary Research Center at the University of North Carolina at Chapel Hill and colleagues. Chronic bronchitis, a common phenotype of chronic obstructive pulmonary disease, is traditionally diagnosed using patient-reported symptoms such as chronic cough and sputum production. These clinical criteria, while widely used, are subjective and may not fully reflect the underlying airway pathology.
Earlier research by the same group demonstrated that total mucin concentration in sputum is an objective marker of chronic bronchitis. In the current study, the investigators sought to improve diagnostic accuracy by incorporating both the amount and composition of airway mucins. To this end, they developed a new metric called the Mucin Quantitative Score (MUCQ), which integrates total mucin concentration with the relative levels of the gel-forming mucins MUC5AC and MUC5B.
The analysis used data from the SPIROMICS (SubPopulations and InteRmediate Outcome Measures in COPD Study) cohort. Participants were classified as having chronic bronchitis or not based on standardized clinical questionnaires. Sputum samples were analyzed to quantify total mucin levels as well as MUC5AC and MUC5B concentrations. These measurements were combined into the MUCQ score, a unitless weighted index reflecting both mucin burden and composition.
The primary objective was to assess whether MUCQ could better classify chronic bronchitis compared with total mucin concentration alone. Patients were first categorized using a predefined total mucin threshold and were then reclassified using a MUCQ cutoff value.
The study led to the following findings:
- Among 164 participants with clinically defined chronic bronchitis, the MUCQ score significantly improved patient classification compared with total mucin concentration alone.
- The MUCQ metric identified additional patients, particularly current smokers, who were not classified as having chronic bronchitis based solely on total mucin levels.
- A small number of individuals previously diagnosed with chronic bronchitis were reclassified as not having the condition when the MUCQ score was applied.
- The overall improvement in patient classification using the MUCQ score was statistically significant.
- MUCQ demonstrated meaningful correlations with other clinical and pathological markers of chronic airway disease.
- The score was associated with indices of airway obstruction, indicating its relevance to functional disease severity.
- These findings suggest that MUCQ captures important aspects of chronic bronchitis severity beyond mucus quantity alone.
The authors concluded that the MUCQ metric is superior to total mucin concentration for distinguishing patients with chronic bronchitis. They noted that prospective trials are needed to determine its role in clinical practice, including disease assessment, monitoring progression, and evaluating therapeutic response.
Reference: DOI: 10.1056/EVIDoa2500051
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