1 Department of Internal Medicine, IRCCS Policlinico San Matteo Foundation, University of Pavia, Pavia, Italy. Electronic address: p.preti@smatteo.pv.it.
2 Department of Internal Medicine, IRCCS Policlinico San Matteo Foundation, University of Pavia, Pavia, Italy.
3 Clinical Epidemiology and Biometry Service. IRCCS Policlinico San Matteo Foundation. Pavia, Italy.