Sputum cytokine repeatability in COPD

<bold>Background:</bold> Immunoassays are commonly used to assess airway inflammation in sputum samples from COPD patients. We have previously validated a Luminex assay able to quantify 20 analytes in sputum supernatant according to current regulatory standards [1]. The repeatability of these biomarkers over time in COPD patients is not known. <bold>Methods:</bold> Biomarkers were measured in paired sputum supernatant samples from COPD patients collected 6 and 12 months apart (n=48 and 18 respectively) using the validated assay. <bold>Results:</bold> 14 panel analytes were detectable. Repeated sputum biomarker measurements showed a significant positive correlation between baseline and 6 months for 13 analytes with intraclass correlation coefficient (ICC) indicating excellent repeatability (>0.75) for 7 analytes (Table 1). Similar results were observed at 12 months. <bold>Conclusion:</bold> This study demonstrates good to excellent repeatability over time in a panel of sputum supernatant biomarkers quantified using a validated Luminex assay. [1] Mulvanny, A et al, Biomedicines 2022; 10, 1949. <bold>Table 1</bold> <table-wrap><object-id>erj;64/suppl_68/PA2994/TB1</object-id><object-id>T1</object-id><object-id>TB1</object-id><table><colgroup><col></col><col></col></colgroup><tbody><tr><td>Analyte</td><td>6 Month Repeatability (<italic>n</italic>=48)</td></tr><tr><td>Correlations (Rho)</td><td>ICC</td></tr><tr><td>IL-1β</td><td>0.62*</td><td>0.78</td></tr><tr><td>IL-1RA</td><td>0.26</td><td>0.42</td></tr><tr><td>IL-2</td><td>0.67*</td><td>0.80</td></tr><tr><td>IL-4</td><td>0.54*</td><td>0.63</td></tr><tr><td>IL-6</td><td>0.50</td><td>0.72</td></tr><tr><td>IL-8</td><td>0.57*</td><td>0.71</td></tr><tr><td>Eotaxin</td><td>0.50</td><td>0.67</td></tr><tr><td>G-CSF</td><td>0.64***</td><td>0.85</td></tr><tr><td>IFN-γ</td><td>0.37*</td><td>0.41</td></tr><tr><td>IP-10</td><td>0.72***</td><td>0.83</td></tr><tr><td>MCP-1</td><td>0.44*</td><td>0.55</td></tr><tr><td>MIP-1α</td><td>0.64*</td><td>0.79</td></tr><tr><td>MIP-1β</td><td>0.72*</td><td>0.86</td></tr><tr><td>TNF-α</td><td>0.57***</td><td>0.79</td></tr></tbody></table><table-wrap-foot> *p<0.01, p<0.001, *p<0.0001 </table-wrap-foot></table-wrap>