1. Instituto e Investigaciones Médico Biológicas de la Universidad Veracruzana, Veracruz, Mexico
2. Gastroenterology Department, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Mexico City, Mexico
3. National Institute of Medical Sciences and Nutrition Salvador Zubirán, Vasco de Quiroga 15, Belisario Domínguez Secc 16, Mexico City 14080, Mexico
4. Ángeles Hospital de Puebla, Puebla, Mexico
5. Hospital Star Médica, Mérida, Yucatán, Mexico
6. Pediatric Gastroenterology Department, Instituto Mexicano del Seguro Social, Mexico City, Mexico
7. Gastroenterology Department, Instituto Nacional de Pediatría, Mexico City, Mexico
8. Gastroenterology Service, Hospital Civil de Guadalajara Fray Antonio Alcalde, Guadalajara, Jalisco, Mexico
9. Gastroenterology Service, Hospital General del Estado Dr. Ernesto Ramos Bours, Hermosillo, Sonora, Mexico
10. Hospital Ángeles Tijuana, Tijuana, Mexico
11. Hospital Médica Sur, Mexico City, Mexico
12. Ambulatory Care Unit Christus Muguerza, San Luis Potosí, S.L.P., Mexico
13. Laboratorios Carnot, Mexico City, Mexico