1. Research Division, Hospital de Especialidades Centro Médico la Raza, Mexico city, Mexico, Rheumatology Department, Hospital de Especialidades Centro Médico la Raza, Mexico city, Mexico,
2. Clinical Epidemiology Research Unit, Hospital de Especialidades Centro Médico la Raza, Mexico city, Mexico
3. Internal Medicine Department, Hospital de Especialidades Centro Médico Nacional Siglo XXI, IMSS, Mexico City, Mexico
4. Clinical Epidemiology Research Unit, Hospital de Especialidades Centro Médico Nacional Siglo XXI, IMSS, Mexico City, Mexico