[1] Ottawa Hosp Res Inst, Ctr Practice Changing Res, Ottawa Hosp Gen Campus,501 Smyth Rd,POB 201B, Ottawa, ON K1H 8L6, Canada
[2] Univ Ioannina, Dept Hyg & Epidemiol, Sch Med, Ioannina 45110, Greece
[3] Sch Social & Community Med, Bristol BS8 2PS, Avon, England
[4] Brown Univ, Ctr Evidence Based Med, Sch Publ Hlth, Providence, RI 02912 USA
[5] Stanford Univ, Sch Med, Stanford Prevent Res Ctr, Stanford, CA 94305 USA
[6] St Michaels Hosp, Li Ka Shing Knowledge Inst, Toronto, ON M5B 1W8, Canada
[7] Amer Coll Physicians, Philadelphia, PA 19106 USA
[8] Spanish Med & Healthcare Prod Agcy, Div Pharmacoepidemiol & Pharmacovigilance, Madrid 28022, Spain
[9] Rigshosp, Nord Cochrane Ctr, Dept 7811, DK-2100 Copenhagen, Denmark
[10] Johns Hopkins Bloomberg Sch Publ Hlth, Baltimore, MD 21205 USA
[11] Univ Paris 05, Ctr Epidemiol Clin, INSERM,Equipe Methodes Evaluat Therapeut Malad, Ctr Rech Epidemiol & Stat,Hop Hotel Dieu,U1153, F-75181 Paris 4, France
[12] Univ Oxford, Nuffield Dept Orthopaed Rheumatol & Musculoskelet, Ctr Stat Med, Botnar Res Ctr, Oxford OX3 7LD, England