1. Respiratory Unit, S. Andrea Hospital, 13100 Vercelli, Italy
2. Laboratory of Pathology, Az. Ospedaliera Maggiore della Carità, 28100 Novara, Italy
3. Allergy and Immunology Unit, Istituti Clinici Scientifici Maugeri IRCCS Pavia, 27100 Pavia, Italy
4. Epidemiological Observatory Service, ASL VC, 13100 Vercelli, Italy
5. Laboratory of Pathology, Department of Traslational Medicine, School of Medicine, University of Eastern Piedmont, 28100 Novara, Italy