1. Center for Effectiveness and Safety Research, Kaiser Permanente, Pasadena, California, USA.
2. Department of Health Systems Science, Kaiser Permanente Bernard J. Tyson School of Medicine, Pasadena, California, USA.
3. Department of Research and Evaluation, Kaiser Permanente Southern California, Pasadena, California, USA.
4. Department of Internal Medicine, Kaiser Permanente Northwest, Portland, Oregon, USA.