A single center case-control study with 100 COPD patients will be organized to compare patients with and without bronchiectasis with regard to the presence of Aspergillus in sputum samples, Aspergillus sensitization and vitamin D. Induced sputum samples will be optimized for culture, Aspergillus galatomannan analysis and RT-PCR.

This study is part of a larger project in which we assume that chronic respiratory infection by Aspergillus fumigatus and the accompanying immune response play an important role in the development of bronchiectasis in COPD. We suspect that this mechanism is controlled by vitamin D and it fails by suppression of the vitamin D receptor by Aspergillus fumigatus.

The present study is designed by the Laboratory of pneumology and will be conducted in collaboration with the Laboratory of clinical bacteriology and mycology of the Catholic University of Leuven.

Inclusion Criteria:

• Established diagnosis of COPD by medical doctor (based on clinical history or pulmonary function test)
• Smoking history of at least 10 pack-years
• CT Thorax available for assessment of bronchiectasis
• FEV1 >= 30%

Exclusion Criteria:

• Mechanical or non-invasive ventilation
• Other main respiratory diagnosis other than COPD
• Active mycobacterial disease
• Immunosuppression other than steroids
• Active cancer treatment

Patients who present in the emergency department with an acute COPD exacerbation (as defined by GOLD executive summary) requiring hospitalization are eligible for this study. Patients should have an established diagnosis of COPD (based on clinical history or pulmonary function test). They will be recruited during their hospital stay in the University Hospital of Leuven.

Additionally, we will include 20 patients with COPD (10 with bronchiectasis versus 10 without) in stable state during their outpatient visits.