1 Department of Rheumatology, Department of Clinical Epidemiology, Leiden University Medical Center, Leiden 2333 ZA, Netherlands. Electronic address: g.kloppenburg@lumc.nl.
2 Department of Family, Community and Emergency Care, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.
3 School of Public Health and Preventive Medicine, Monash University, Melbourne, VIC, Australia; Department of Rheumatology, Alfred Hospital, Melbourne, VIC, Australia.