[1] Hosp Infantil Mexico Dr Federico Gomez, Secretaria Salud, Evidence Based Med Res Unit, Mexico City, DF, Mexico
[2] Hosp Reg 72 Tlalnepantla, Inst Mexicano Seguro Social, Dept Pediat, Mexico City, DF, Mexico
[3] Ctr Med Occidente, Inst Mexicano Seguro Social, Guadalajara, Jalisco, Mexico
[4] Hosp Angeles, Clin Londres, Dept Cardiol, Mexico City, DF, Mexico
[5] Inst Nacl Salud Publ, Cuernavaca, Morelos, Mexico
[6] IMSS, Hosp Epidemiol Res Unit, Hlth Res Coordinat, Av Cuauhtemoc 330, Mexico City 06720, DF, Mexico