Terttu Harju1,2
, Witold Mazur3
, Heta Merikallio1,2
, Ylermi Soini4,5
and Vuokko L Kinnula3 
1Institute of Clinical Medicine, Department of Internal Medicine, Centre of Excellence in Research, P. O. Box 5000, 90014 University of Oulu, Oulu, Finland
2Department of Internal Medicine, Clinical Research Center, Oulu University Hospital, Oulu, Finland
3Department of Medicine, Division of Pulmonary Diseases, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
4Department of Pathology, Oulu University Hospital, Oulu, Finland
5Department of Clinical Pathology and Forensic Medicine, University of Kuopio, Kuopio, Finland