[1] Chung Shan Med Univ, Inst Med, Taichung 402, Taiwan
[2] Show Chwan Mem Hosp, Dept Otolaryngol Head & Neck Surg, Changhua 500, Taiwan
[3] Chang Bin Show Chwan Mem Hosp, Dept Otolaryngol, Changhua 505, Taiwan
[4] Chwan Mem Hosp, Dept Pathol, Changhua 500, Taiwan
[5] Chung Shan Med Univ, Dept Publ Hlth, Taichung 402, Taiwan
[6] Changhua Christian Hosp, Dept Otorhinolaryngol Head & Neck Surg, Changhua 500, Taiwan
[7] Chung Shan Med Univ Hosp, Dept Med Res, Taichung 402, Taiwan