[1] Massachusetts Gen Hosp, Harvard Med Sch, Dept Emergency Med, 125 Nashua St,Ste 920, Boston, MA 02114 USA
[2] Monash Univ, Fac Med Nursing & Hlth Sci, Sch Clin Sci, Dept Paediat, Clayton, Vic, Australia
[3] Murdoch Childrens Res Inst, Emergency Res, Parkville, Vic, Australia
[4] Monash Med Ctr, Monash Hlth, Paediatr Emergency Dept, Monash Emergency Serv, Clayton, Vic, Australia
[5] Natl Childrens Hosp, Div Emergency Med, Washington, DC 20010 USA
[6] Massachusetts Gen Hosp, Harvard Med Sch, Dept Med, Divis Rheumatol Allergy & Immunol, Boston, MA 02114 USA