1. Department of Internal Medicine, Azienda Ospedaliera Universitaria San Martino, Genoa
2. Epidemiology and Statistics Unit, IRCCS G. Gaslini, Genoa
3. Pneumology and Allergy Center, IRCCS G. Gaslini, Genoa
4. Pneumology and Allergy, Navy Medical Service, La Spezia
5. Clinica Pediatrica, Foundation IRCCS San Matteo, University of Pavia, Pavia, Italy