1 Department of Clinical and Experimental Medicine, University of Catania, Catania, Italy; Respiratory Medicine Unit, Policlinico "G. Rodolico-San Marco" University Hospital, Catania, Italy.
2 Respiratory Medicine Unit, Policlinico "G. Rodolico-San Marco" University Hospital, Catania, Italy.
3 Department of Clinical and Experimental Medicine, University of Catania, Catania, Italy.
4 Department of Clinical and Experimental Medicine, University of Catania, Catania, Italy; Respiratory Medicine Unit, Policlinico "G. Rodolico-San Marco" University Hospital, Catania, Italy. Electronic address: claudia.crimi@unict.it.