[1] Univ Tsukuba, Fac Med, Dept Internal Med, Tennodai 1-1-1, Tsukuba, Ibaraki 3058575, Japan
[2] Univ Tsukuba, Fac Med, Dept Otolaryngol, Tennodai 1-1-1, Tsukuba, Ibaraki 3058575, Japan
[3] Univ Tsukuba, Fac Med, Dept Diagnost Pathol, Tennodai 1-1-1, Tsukuba, Ibaraki 3058575, Japan