[1] Hosp Univ Canarias, Div Rheumatol, Tenerife, Spain
[2] Hosp Univ Canarias, Cent Lab Div, Tenerife, Spain
[3] IDIVAL, Div Rheumatol, Epidemiol Genet & Atherosclerosis Res Grp Syst In, Santander, Spain
[4] IDIVAL, Hosp Univ Marques de Valdecilla, Div Rheumatol, Santander, Spain
[5] Univ Witwatersrand, Johannesburg, South Africa