S28 Non-invasive nasal sampling using nasosorption may identify COPD inflammatory profiles and have a role as a diagnostic tool in exacerbations

<h3></h3> COPD is a heterogenous disease and there is ongoing need to identify biomarkers for treatable endotypes. Nasosorption is a non-invasive and safe way of sampling the respiratory tract to obtain undiluted endothelial lining fluid. This study investigates whether nasosorption can be used to characterise COPD. Nasosorption was performed on 23 non-smokers and 32 COPD patients and MSD (Mesoscale Discovery) used to measure an array of cytokines. IL-4 (NSm:3.06±1.49ng/ml, COPD:0.07±0.03ng/ml), IL-5 (NSm:8.2±2.51ng/ml, COPD:2.03±0.66ng/ml), IL-6 (NSm:20.00±2.73ng/ml, COPD:12.89±2.73ng/ml), CXCL-8 (NSm:4729.2±703.7ng/ml, COPD:2378.3±404.6ng/ml) and IFNγ (NSm:108.37±46.81ng/ml, COPD: 12.93±11.17ng/ml) were significantly lower in COPD than non-smokers. Eotaxin was higher in COPD (NSm:2.90±0.57ng/ml, COPD:6.53±1.12ng/ml). The COPD cohort was further analysed to look at commonly identified clinical phenotypes. Nasal eotaxin was raised in the high blood eosinophil cohort (&gt;300cells/100µl) compared to low eosinophil cohort (7.93±2.66ng/ml vs 2.91±1.14ng/ml, p&lt;0.05), but other TH2 cytokines such as IL-4, IL-5, IL-13 did not differ. 16% of COPD patients had co-existing bronchiectasis. These patients had significantly higher nasal IL-7 (109.7±6.0ng/ml vs 56.9±7.9ng/ml, p&lt;0.05), CXCL10 (4446.0±1540.0ng/ml vs 949.5±237.7ng/ml, p&lt;0.01), CXCL11 (6.41±5.32ng/ml vs 0.30±0.9ng/ml, p&lt;0.01) and CCL17 (56.1±6.8ng/ml vs 32.3±4.1ng/ml, p&lt;0.05). Comparing frequent (≥2 exacerbations/year) against infrequent exacerbators (&lt;2/year) there were non-significant trends of increased IL-6 (15.7±4.1ng/ml vs 7.68±2.81ng/ml) and reduced IL-13 (8.8±3.1ng/ml vs 17.9±3.9ng/ml) and IL-33(63.8±23.2ng/ml vs 144.1±63.1ng/ml) in frequent exacerbators. 16 COPD patients were sampled at exacerbation and &gt;4 weeks after recovery. IFNγ was higher during exacerbation than on recovery (729.6±591.2ng/ml vs 2.2±1.3ng/ml, p&lt;0.05), with a trend towards higher levels in viral vs non-viral exacerbations. Other markers known to be associated with viral infections such as IFNα, CXCL10 and TSLP were non-significantly increased in viral vs non-viral exacerbations. There was also a trend towards eotaxin levels being raised during exacerbation, with higher levels in non-bacterial rather than bacterial exacerbations (Non-bact:4.02±2.57ng/ml, Bact: 3.46±1.48ng/ml, p&lt;0.05). We show that nasosorption may identify differences in inflammatory profiles in COPD. As a non-invasive test, its potential for qualifying exacerbations in a less stable patient is particularly relevant. A larger study is needed to cohort COPD phenotypes based on nasal inflammation and assess its use as a diagnostic test during exacerbations.