Late Breaking Abstract - High blood neutrophils are associated with increased exacerbations and mortality in Chronic Obstructive Pulmonary Disease

<b>Introduction:</b> Identifying patients with COPD at increased risk of adverse events is challenging due to disease heterogeneity. Routine clinical measurements could offer a way to identify such people. <b>Methods:</b> In a large population-based COPD registry in the East of Scotland (TARDIS: Tayside Allergic and Respiratory Disease Information System), blood neutrophil counts (BNC) were compared to sputum neutrophil counts, measures of disease severity and mortality. Exacerbation frequency was examined using negative binomial regression models, mortality was assessed by Cox proportional hazards models, and FEV1 decline was evaluated by mixed effects models. <b>Results:</b> 113,424 neutrophil counts were obtained from 4579 people (mean follow up 10 years, range 1-17) during stable disease periods. Median BNC was 5800cells/µL (IQR 4200-8300). Mortality rates among the 35% with BNC &gt;6000cells/µL at the study start were 80% higher (13.8/100 person years v 7.4/100py; p&lt;0.001) than those &lt;6000. People with high BNC were more likely to be classified as GOLD D (45% v 33% p&lt;0.001) and had more exacerbations (mean 1.7 v 1.3/year; p&lt;0.001) and severe exacerbations (mean 0.3 v 0.1/year; p&lt;0.001). Eosinophil counts were much less predictive of these outcomes. In a subcohort, blood and sputum neutrophils showed a moderate correlation. No relationship between BNC and subsequent rate of FEV1 decline was identified. Similar results were obtained after adjusting for covariates, and in analyses that focused on the later stages of disease progression. <b>Conclusions:</b> High BNC may provide a useful indicator of risk of exacerbations and mortality in COPD patients.