Decreased serum club cell secretory protein in asthma and chronic obstructive pulmonary disease overlap: A pilot study

Purpose: Improvement in the diagnosis of asthma and chronic obstructive pulmonary disease (COPD) overlap (ACO), and identification of biomarkers for phenotype recognition will encourage good patient care by providing optimal therapy. We investigated club cell secretory protein (CC-16), a protective and anti-inflammatory mediator, as a new candidate biomarker for diagnosing ACO. Patients and methods: We performed a multicenter cohort study. A total of 107 patients were divided into three groups - asthma, COPD, and ACO - according to the Spanish guidelines algorithm, and enrolled into the study. Serum CC-16 levels were measured using commercial ELISA kits. Results: Serum CC-16 levels were the lowest in patients with ACO. Low serum CC-16 levels were a significant marker for the ACO even after adjustment for age, sex, and smoking intensity. Serum CC-16 levels were positively correlated with forced expiratory volume in 1 second (FEV ₁ ), forced vital capacity (FVC), forced expiratory flow at 25%-75% of FVC, FEV ₁ /FVC, vital capacity, and diffusing capacity of the lung for carbon monoxide, and were negatively correlated with smoking amount (pack-years), bronchodilator response, fractional residual capacity, residual volume, and number of exacerbations per year. FEV ₁ and serum CC-16 levels were significantly lower in patients with frequent exacerbations. Conclusion: Serum CC-16 has the potential to be a biomarker for ACO diagnosis and also treat frequent exacerbations in patients with chronic inflammatory airway diseases.