Sputum Cytokine Repeatability in COPD.

Introduction: Sputum biomarker measurements are used to measure airway inflammation in COPD patients. We have previously validated a Luminex assay able to quantify 15 analytes in COPD sputum supernatant. This assay demonstrated sputum protein expression profiles associated with neutrophilia, airway bacterial colonisation and current smoking in COPD. Methods: We report repeat sputum supernatant analysis at 6 months from a sub-group of COPD patients who participated in the original study. 48 COPD patients provided a repeat sputum sample at 6 months. 15 panel analytes were detectable. Results: Repeated sputum cytokine measurements showed a significant positive correlation between baseline and 6 months for all analytes except IL-1RA with intraclass correlation coefficient (ICC) indicating good to excellent repeatability. IL-1β, IL-2, IL-8, IL-17A, G-CSF, MIP-1α, MIP-1β and TNF-α were significantly correlated with sputum neutrophil percentage at 6 months. IL-1β, IL-4, IL-8 and G-CSF were significantly increased in Haemophilus influenzae colonised patients and IL-1β, IL-4, IL-8, G-CSF, IFN-γ, IP-10, MCP-1, MIP-1α, MIP-1β and TNF-α were significantly higher in ex-smoking COPD patients. Discussion: A multiplex immunoassay used at repeated visits in COPD patients showed a high degree of reproducibility for the majority of analytes. There were reproducible inflammatory signatures in sputum associated with clinical characteristics in COPD patients.