1. Department of General Pathology, General Hospital No. 16, Mexican Institute of Social Security (IMSS), Torreon, Coahuila, Mexico
2. Department of Pediatric Gastroenterology and Nutrition, Medical High Specialty Unit (UMAE) No. 71, IMSS, Torreon, Coahuila, Mexico
3. Clinical Epidemiology Research Unit, Medical High Specialty Unit (UMAE) No. 71, IMSS, Torreon, Coahuila, Mexico
4. Biomedic Research Center, School of Medicine, Universidad Autonoma de Coahuila, Torreon, Coahuila, Mexico