title: [Hierarchical regionalization for spatial epidemiology: a case study of thyroid cancer incidence in Yiwu, Zhejiang].
abstract: OBJECTIVE
  Sporadic cases occurring in mall geographic unit could lead to extreme value of incidence due to the small population bases, which would influence the analysis of actual incidence.
  
  
  METHODS
  This study introduced a method of hierarchy clustering and partitioning regionalization, which integrates areas with small population into larger areas with enough population by using Geographic Information System (GIS) based on the principles of spatial continuity and geographical similarity (homogeneity test). This method was applied in spatial epidemiology by using a data set of thyroid cancer incidence in Yiwu, Zhejiang province, between 2010 and 2013.
  
  
  RESULTS
  Thyroid cancer incidence data were more reliable and stable in the new regionalized areas. Hotspot analysis (Getis-Ord) on the incidence in new areas indicated that there was obvious case clustering in the central area of Yiwu.
  
  
  CONCLUSIONS
  This method can effectively solve the problem of small population base in small geographic units in spatial epidemiological analysis of thyroid cancer incidence and can be used for other diseases and in other areas.
authors.affiliation: Yiwu Center for Disease Control and Prevention, Yiwu 322000, China.
authors.forename: Shizhu
authors.initials: S
authors.lastname: Teng
authors.affiliation: Yiwu Center for Disease Control and Prevention, Yiwu 322000, China; Email: 605515026@qq.com.
authors.forename: Qiaojuan
authors.initials: Q
authors.lastname: Jia
authors.affiliation: Yiwu Center for Disease Control and Prevention, Yiwu 322000, China.
authors.forename: Yijian
authors.initials: Y
authors.lastname: Huang
authors.affiliation: Yiwu Center for Disease Control and Prevention, Yiwu 322000, China.
authors.forename: Liangcao
authors.initials: L
authors.lastname: Chen
authors.affiliation: College of Environmental and Resource Sciences, Zhejiang University.
authors.forename: Xufeng
authors.initials: X
authors.lastname: Fei
authors.affiliation: College of Environmental and Resource Sciences, Zhejiang University.
authors.forename: Jiaping
authors.initials: J
authors.lastname: Wu
mesh_terms: D002681:China / Q000453:epidemiology; D016000:Cluster Analysis; D062665:Epidemiological Monitoring; D040362:Geographic Information Systems; D005843:Geography; D006801:Humans; D015994:Incidence; D062206:Spatial Analysis; D013964:Thyroid Neoplasms / Q000453:epidemiology*