1. University of Pavia, Istituti Clinici Scientifici Maugeri, Pavia, Italy.
2. Epidemiology Unit, Italian Society for Rheumatology, Milan, Italy.
3. Epidemiology Unit, Italian Society for Rheumatology, Milan, and Department of Statistics and Quantitative Methods, Division of Biostatistics, Epidemiology and Public Health, University of Milano-Bicocca, Milan, Italy.
4. Epidemiology Unit, Italian Society for Rheumatology, Milan, and School of Medicine and Surgery, University of Milano-Bicocca, Milan, Italy. c.scire@reumatologia.it
5. Department of Rheumatology, Fondazione IRCCS Policlinico San Matteo, Pavia, Italy.