[1] La Fe Childrens Hosp, Pediat Gastroenterol Unit, Valencia, Spain
[2] Nuestra Sra Candelaria Univ Hosp, Pediat Gastroenterol Unit, Tenerife, Spain
[3] Inst Invest Med Dr Alfredo Lanari, Pediat Gastroenterol Unit, Buenos Aires, DF, Argentina
[4] Canary Univ Hosp, Pediat Gastroenterol Unit, Las Palmas Gran Canaria, Spain
[5] Pereira Rosell Hosp, Pediat Gastroenterol Unit, Montevideo, Uruguay
[6] Pereira Rosell Hosp, Clin Immunol Lab, Montevideo, Uruguay
[7] Doce Octubre Hosp, Pediat Gastroenterol Unit, Madrid, Spain
[8] Natl Biotechnol Ctr, Madrid, Spain