[1] Univ Nacl Autonoma Mexico, Unidad Epidemiol, Clin HIMFG, Fac Med, Mexico City, DF, Mexico
[2] IRO, Buenos Aires, DF, Argentina
[3] Univ Fed Sao Paulo, Sao Paulo, Brazil
[4] Cent Univ Venezuela, Caracas, Venezuela
[5] Hosp Cosme Argerich, Serv Reumatol, Buenos Aires, DF, Argentina
[6] Clin Kennedy Alborada, Ctr Reumatol & Rehabil, Guayaquil, Ecuador
[7] Hosp Apoyo Maria Auxiliadora, Serv Reumatol, Lima, Peru