CAT score single item analysis in patients with COPD: results from COSYCONET - von Siemens, M; Alter, P; Lutter, J; Kauczor, HU; Jobst, BJ; Bals, R; Trudzinski, FC; Söhler, S; Behr, J; Watz, H; Waschki, B; Bewig, B; Jones, P; Welte, T; Vogelmeier, C; Jörres, R; Kahnert, K (Pneumologie, 2020)