Chronic obstructive pulmonary disease (COPD) exacerbations are a common cause of respiratory morbidity and mortality, and have various etiologies. Multiple cellular and molecular biomarkers have been associated with exacerbations. Quantitative sputum cell counts are able to identify the presence and type of bronchitis, which is an important contributor to exacerbations. Their utility to monitor bronchitis and to help treat exacerbations has been evaluated, yet they are not used in routine clinical practice. Areas covered: This review will provide a brief summary of biomarkers utilized in COPD, with a focus on the application of cellular markers for the management of exacerbations. A case study will demonstrate the application of these methods. With quantitative sputum cell counts, the presence of eosinophilic bronchitis predicts corticosteroid-responsiveness, while neutrophilic bronchitis identifies infection and suggests the need for antibiotics. Gastroesophageal reflux-related aspiration and heart failure can also be identified by examining sputum. Expert commentary: Quantitative sputum cytometry is an essential tool in the management of exacerbations of COPD, particularly those prone to frequent exacerbations. Treatment based on sputum cell counts is superior to current guideline-based recommendations to prevent future exacerbations and hospitalizations in observational and single-centre controlled trials. Large multicentre clinical trials are necessary to confirm this.
Keywords: Biomarkers; COPD exacerbations; bronchitis; endotype; eosinophils; sputum cell counts.