[1] Metroplex Clin Res Ctr, Dallas, TX USA
[2] Inst Invest Hosp, Madrid, Spain
[3] Amgen Inc, Thousand Oaks, CA USA
[4] Abt Nephrol & Rheumatol, Gottingen, Germany
[5] Altoona Ctr Clin Res, Duncansville, PA USA
[6] Arthrit & Rheumatism Associates, Wheaton, IL USA