1. Department of Pediatrics, Obihiro Kyoukai Hospital, Obihiro 080-0805, Japan
2. Department of Pediatrics Hokkaido University School of Medicine, Sapporo 060-8638, Japan
3. Central Clinical Laboratories, Keio University Hospital, Tokyo, 160-8582, Japan
4. Department of Pediatrics , Keio University School of Medicine, Tokyo 160-8582, Japan