1. VA Palo Alto Health Care System , Palo Alto, CA 94025, United States
2. Department of Health Policy, Stanford University School of Medicine , Stanford, CA 94305, United States
3. Carolina Health Informatics Program, University of North Carolina at Chapel Hill (UNC) , Chapel Hill, NC 27599, United States
4. School of Nursing, UNC , Chapel Hill, NC 27599, United States
5. Division of General Internal Medicine, Department of Medicine, Feinberg School of Medicine, Northwestern University , Chicago, IL 60611, United States
6. Department of Biostatistics & Bioinformatics, Duke School of Medicine , Durham, NC 27710, United States