1 WHO Collaborating Centre for Tuberculosis and Lung Diseases, Fondazione S Maugeri, Care and Research Institute, Tradate 21049, Italy. Electronic address: giovannibattista.migliori@fsm.it.
2 Epidemiology and Medical Statistics Unit, Department of Biomedical Sciences, University of Sassari-Research, Medical Education and Professional Development Unit, AOU Sassari, Italy.