1. University of Modena and Reggio Emilia; Statistics Unit, Department of clinical and diagnostic medicine and public health, University of Modena and Reggio Emilia, Modena, Italy; Via del Pozzo 71 Modena Italy 41121
2. Policlinico San Matteo, Pavia; Via F. Sporza 35 Milano Italy 20122
3. Mario Negri Institute; Laboratorio di Epidemiologia Clinica; Via Eritrea 62 Milano Milano Italy 20157
4. Università degli Studi di Sassari; Dipartimento di Scienze Chirurgiche, Microchirurgiche e Mediche; Via le San Peitro, 43 - Palazzo Clemente Sassari Italy 07100
5. University of Modena and Reggio Emilia; Department of Oncology, Hematology and Respiratory Diseases; Via del Pozzo 71 Modena Italy 41100
6. Mario Negri Institute for Pharmacological Research; Italian Cochrane Centre; Via La Masa, 19 Milan Italy 20156