1. Department of Analytical Biochemistry, Groningen Research Institute of Pharmacy (GRIP) , University of Groningen , Groningen , The Netherlands
2. Department of Pulmonary Diseases , University Medical Center Groningen, University of Groningen , Groningen , The Netherlands
3. Groningen Research Institute for Asthma and COPD (GRIAC) , University Medical Center Groningen, University of Groningen , Groningen , The Netherlands