1. Section of Pulmonary, Critical Care, Allergy and Immunology, Department of Internal Medicine, Wake Forest Baptist Medical Center, Winston-Salem, NC, USA
2. Department of Biostatistics and Epidemiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
3. Pulmonary, Allergy, and Critical Care Division, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
4. Center for Clinical Epidemiology and Biostatistics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA