1. From the Department of Pathology, Phoenix Children's Hospital, Phoenix, Ariz (Drs Carpentieri and Dickman); the Department of Laboratory Medicine, Children's Hospital, Columbus, Ohio (Dr Qualman and Mr Bowen); the Department of Pathology, University of Chicago Hospitals, Chicago, Ill (Dr Krausz); and the Department of Pathology, Cedars-Sinai Medical Center, Los Angeles, Calif (Dr Marchevsky)