Sputum Cytokine Repeatability in COPD

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.

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.

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.

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.