Validation of sputum supernatant biomarker assays in stable and exacerbating COPD subjects

<b>Background:</b> Induced sputum is a non-invasive technique used to assess airway inflammation. Sputum supernatant biomarker measurements may be prone to variability due to multiple factors, including matrix interference and poor analyte recovery. It is important to comprehensively validate sputum supernatant assays for use in clinical studies. <b>Aims and Objectives:</b> We validated commonly used COPD sputum supernatant biomarkers as per recommendations in current international guidelines. The assays were used to evaluate differences between COPD patients and controls, and changes during exacerbations. <b>Methods:</b> Assay validation involved assessment of immunological similarities between recombinant reference material and endogenous biomarker, diluent suitability, effect of dilution on analyte recovery, calibration curve establishment, assay selectivity and reproducibility, limits of quantification and stability. Sputum MPO, IL-1β, IL-6, IL-8 and TNF-α were measured in 34 COPD subjects, 14 paired exacerbation samples, 20 healthy smokers and non-smokers. <b>Results:</b> All assays demonstrated acceptable precision and reproducibility. All cytokines were increased in COPD vs controls. IL-1β, IL-6 and TNF-α were significantly increased during exacerbations (Table 1). <b>Conclusion:</b> We successfully validated a panel of sputum biomarkers, able to differentiate between COPD and controls and were changed during exacerbation.