1. Center for Health Equity Research and Promotion, Corporal Michael J. Crescenz Veterans Affairs Medical Center, 3900 Woodland Avenue, Philadelphia, PA 19104, USA.
2. Department of Medical Ethics and Health Policy, University of Pennsylvania, 3401 Market Street, Philadelphia, PA 19104, USA.
3. Department of Medicine, University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA 19104, USA.
4. Department of Health Care Management, University of Pennsylvania, 3641 Locust Walk, Philadelphia, PA 19104, USA.
5. Department of Biostatistics and Epidemiology, University of Pennsylvania, 423 Guardian Drive, Philadelphia, PA 19104, USA.