[1] Univ Concepcion, Fac Med, Dept Especialidades, Concepcion, Chile
[2] Univ Concepcion, Dept Pediat, Concepcion, Chile
[3] Univ Concepcion, Dept Med Interna, Concepcion, Chile
[4] Hosp Guillermo Grant Benavente, Concepcion, Chile
[5] Univ Austral Chile, Valdivia, Chile
[6] Inst Salud Publ Chile, Santiago, Chile