[1] Capital Med Univ, Beijing Childrens Hosp, Dept Otolaryngol, Beijing, Peoples R China
[2] Capital Med Univ, Dept Stat, Beijing, Peoples R China
[3] Beijing Maternal & Child Hlth Care Hosp, Beijing, Peoples R China
[4] Capital Med Univ, Da Xing Hosp, Beijing, Peoples R China
[5] Natl Univ Singapore, Yong Loo Lin Sch Med, Biostat Unit, Singapore 119228, Singapore
[6] Natl Univ Singapore, Yong Loo Lin Sch Med, Dept Otolaryngol, Singapore 119228, Singapore