1. Department of General Medicine, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8558, Japan
2. Department of General Internal Medicine, Okinawa Chubu Hospital, Uruma 904-2243, Japan
3. Department of Diagnostic and Generalist Medicine, Dokkyo Medical University, Shimotsuga, Tochigi 321-0293, Japan
4. Department of Primary Care and Medical Education, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8558, Japan