1. Department of Health Services Research, Institute of Medicine, University of Tsukuba, Tsukuba 305-8575, Ibaraki, Japan
2. Medical English Communications Center, Institute of Medicine, University of Tsukuba, Tsukuba 305-8575, Ibaraki, Japan
3. Department of Health Services Research, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba 305-8575, Ibaraki, Japan
4. Health Services Research and Development Center, University of Tsukuba, Tsukuba 305-8575, Ibaraki, Japan
5. Hinohara Memorial Peace House Hospital, Nakai 259-0151, Kanagawa, Japan
6. Department of Medicine, Stanford University, Stanford, CA 94305, USA