1. Division of Research, Kaiser Permanente Northern California , Oakland, California , USA
2. Department of Research and Evaluation, Kaiser Permanente Southern California , Pasadena, California , USA
3. Department of Health Systems Science, Kaiser Permanente Bernard J. Tyson School of Medicine , Pasadena, California , USA
4. Mid-Atlantic Permanente Research Institute, Kaiser Permanente Mid-Atlantic States , Rockville, Maryland , USA
5. Department of Population Medicine, Harvard Medical School and Harvard Pilgrim Health Care Institute , Boston, Massachusetts , USA
6. Department of Clinical Science, Kaiser Permanente Bernard J. Tyson School of Medicine , Pasadena, California, USA
7. Department of Epidemiology and Biostatistics, University of California , San Francisco, California , USA