title: Measuring the geographic coverage of methadone maintenance programme in Hong Kong by using geographic information system (GIS).
abstract: OBJECTIVE
  While access and utilization form core components in assessing the effectiveness of a health service, the concept of coverage is often neglected. In this study we propose to develop a GIS-based methodological framework for the measurement of district-based geographic coverage to examine the service effectiveness of methadone treatment programme (MTP) in Hong Kong on a regular basis.
  
  
  METHODS
  To overcome the incompatibility of spatial units, population data and data of heroin addiction of the year 2001 are interpolated by population-weighted and area-weighted algorithms. Standard overlay and proximity analytical functions are used to delineate altogether 20 accessible zones around each methadone clinic at a fixed 1.5 km Euclidean distance. Geographic coverage here is defined as the percentage of heroin addicts covered by a methadone clinic within the accessible zone by district.
  
  
  RESULTS
  A total of 6413 out of 11000 reported heroin addicts are found geographically covered. The average geographic coverage in Hong Kong is 44.6%, with the figure varying from 0% to 96% by district. One district having no clinic results in 0% coverage whereas another without a clinic yields 15.3% coverage from the clinic in adjacent district. Maps illustrating district-based geographic coverage are generated.
  
  
  CONCLUSIONS
  As continuous data collection is required for a monitoring system, the simplified approach facilitates the handling of large volume data and relevant data analysis. It is concluded that the number of methadone clinics is as important as their locations. Geographic coverage could become an important consideration for monitoring harm reduction.
authors.affiliation: Stanley Ho Centre for Emerging Infectious Diseases, The Chinese University of Hong Kong, Shatin, Hong Kong, China. ppang@cuhk.edu.hk
authors.forename: Tak Ting P
authors.initials: TT
authors.lastname: Pang
authors.forename: Shui Shan
authors.initials: SS
authors.lastname: Lee
mesh_terms: D000701:Analgesics, Opioid / Q000627:therapeutic use*; D003625:Data Collection; D040362:Geographic Information Systems; D006297:Health Services Accessibility; D006556:Heroin Dependence / Q000534:rehabilitation; D006723:Hong Kong; D006801:Humans; D008691:Methadone / Q000627:therapeutic use*; D016320:Substance Abuse Treatment Centers; D019371:Topography, Medical
chemical_list: D000701:Analgesics, Opioid; D008691:Methadone