Author contributions
Conception and design: Koji Izutsu, Hideyuki Honda, Sumiko Okubo. Provision of study materials or patients: Hideki Goto, Koji Izutsu, Satoshi Ito, Masahiro Kizaki, Masaki Yamaguchi, Noriko Fukuhara, Koji Kato, Toko Saito. Collection and assembly of data: Sumiko Okubo, Tomomi Soshin, Jiewei Zeng, Mohamed Badawi, Jeremy Ross. Data analysis and interpretation: All authors. Manuscript writing: All authors. Final approval of manuscript: All authors.