1 Department of Pediatrics and Emergency Medicine, Perelman School of Medicine at the University of Pennsylvania, Children's Hospital of Philadelphia (D Cullen and J Fein), Philadelphia, Pa. Electronic address: CullenDL@chop.edu.
2 Department of Population Health, Children's Hospital of Philadelphia (L Wilson-Hall), Philadelphia, Pa.
3 Department of Clinical Pediatrics, Perelman School of Medicine at the University of Pennsylvania, Children's Hospital of Philadelphia (K McPeak), Philadelphia, Pa.
4 Department of Pediatrics and Emergency Medicine, Perelman School of Medicine at the University of Pennsylvania, Children's Hospital of Philadelphia (D Cullen and J Fein), Philadelphia, Pa.