Reference	Objective	Design	Evidence
Groenewegen and Wouters [157]	To study bacterial infections in COPD exacerbated patients that need hospitalization	PCS	3C+
Ko et al. [160]	To study sputum microbiology in AECOPD	PCS	4C+
Rosell et al. [169]	To study the microbiological determinants of AECOPD	MA	1A+
Lin et al. [464]	To study the microbiology of AECOPD	PCS	3B+
Montero et al. [465]	To study the association between multi‐resistant P. aeruginosa and outcome of AECOPD	CCS	4b+