1. University of California San Francisco, Department of Medicine, Division of General Internal Medicine, San Francisco General Hospital, San Francisco, CA, USA
2. University of California San Francisco, Center for Vulnerable Populations, San Francisco, CA, USA
3. Kaiser Permanente Northern California, Division of Research, Oakland, CA, USA
4. Group Health Research Institute, Seattle, WA, USA
5. Kaiser Permanente, National Market Research, Oakland, CA, USA