1. Department of Hematology, Hakodate Municipal Hospital, 1–10-1 Minato-cho, Hakodate 041-8680, Japan
2. Department of Clinical Pathology, Hakodate Municipal Hospital, 1–10-1 Minato-cho, Hakodate 041-8680, Japan
3. Department of Hematology and Oncology, Hokkaido University Graduate School of Medicine, Sapporo 60-8638, Japan
4. Department of Gastroenterology, Hokkaido University Graduate School of Medicine, Sapporo 60-8638, Japan