COPD and the asthma-COPD-overlap-syndrome

In clinical practice separating asthma from COPD may be difficult due to overlapping clinical and functional features common to both diseases. To characterize the Asthma-COPD-Overlap-Syndrome (ACOS), 108 consecutive former or current smokers with physician-diagnosed COPD [mean age 65,5±8,5 yrs., 45,4% female, 21,3% smokers (55,3±25,8 py), 78,7% ex-smokers (53,0±32,5 py), FEV1 (postBD) 58,0±20,0%, diffusion capacity (DLCO) median 47,5% IQR 38,0%-64,0%] were prospectively recruited in 2012 and 2013 and evaluated for 11 pre-specified asthma features by history including standardized questionnaires, lung function and allergy tests, serum IgE levels, blood and induced sputum differential cell counts, and FeNO. 35 patients (32,4%) fulfilled at least one, 1 patient 8 asthma criteria. Based on typical asthma features 25,9% of patients were classified by three blinded experts (TS, SK,RB) as ACOS [mean age 64,3±11,2 y; 57,1% female; 21,4% smokers (32,5±17,8 py); FEV1 (postBD) 65,0±19,0%, DLCO median 65,3% IQR: 43,0%-75,8%]. Similarly, a score for ACOS diagnosis using asthma and COPD criteria was highly concordant with clinical judgment (AUC 0,944). Compared with the 'pure' COPD population, ACOS patients (had) smoked less (p<0,001), were more often atopic (p<0,001), had more peripheral eosinophils (p=0,042), had similar lung function before bronchodilator (p=0,163), but with a higher reversibility (p=0,006) and a better diffusion capacity (p=0,003). In conclusion, established diagnostic asthma and COPD criteria are able to characterize COPD and ACOS patients.