1 Division of General Medicine and Clinical Epidemiology, Department of Medicine, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill.
2 Cecil G. Sheps Center for Health Services Research, University of North Carolina at Chapel Hill, Chapel Hill.
3 Division of General Pediatrics and Adolescent Medicine, Department of Pediatrics, University of North Carolina at Chapel Hill, Chapel Hill.
4 Department of Pediatrics, Wake Forest School of Medicine, Winston-Salem, North Carolina.
5 Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina.