1 Division of Rheumatology, Hospital Universitario de Canarias, Tenerife, Spain.
2 Central Laboratory Division, Hospital Universitario de Canarias, Tenerife, Spain.
3 Epidemiology, Genetics and Atherosclerosis Research Group on Systemic Inflammatory Diseases, Hospital Universitario Marqués de Valdecilla, IDIVAL, Santander, Spain.
4 Division of Rheumatology, Hospital Universitario Marqués de Valdecilla, IDIVAL, Santander, Spain; and University of the Witwatersrand, Johannesburg, South Africa.