Terashima Mikiko, Kephart George
School of Planning, Department of Community Health and Epidemiology, Healthy Populations Institute, Dalhousie University, Halifax, NS.
Can J Public Health. 2016 Dec 27;107(4-5):e424-e430. doi: 10.17269/cjph.107.5459.
Postal codes are often the only available geographic identifiers in many sources of health data in Canada. In order to conduct geographic analyses, postal codes are routinely geocoded to census geography to link to ecological data. Despite common use of this method, the extent of geographic misclassification errors is poorly understood. We estimated misclassification errors in the geocoding of postal codes to assign census geography in Nova Scotia, Canada.
We examined differences between counts and match rates for postal-code geocoded and actual locations of buildings in Nova Scotia at two census administrative area levels: dissemination areas (DAs) and census subdivisions (CSDs). Actual locations were based on the data collected by the provincial government containing actual latitude/longitude of buildings. Variation in misclassification by rurality, using Statistics Canada's classification, was also assessed.
Outside two urban areas (Halifax Metro and Sydney) which had <10% differences in counts, many DAs had >30% differences. Match rates showed similar patterns, with the vast majority of non-urban DAs having <40% match rates. Even in major urban areas, 10% of DAs had large misclassification errors. Misclassification errors at the CSD level were still too great to estimate counts or rates without further area aggregation.
Routine use of postal code geocoding should be replaced with geocoding of location information using additional identifiers such as civic addresses or latitude and longitude. If data holders did this in-house before providing data to researchers, the accuracy and capacity of geographic analysis would be enhanced while protecting confidentiality.
在加拿大许多健康数据来源中，邮政编码往往是唯一可用的地理标识符。为了进行地理分析，邮政编码通常会被地理编码到人口普查地理区域，以便与生态数据相链接。尽管这种方法被广泛使用，但地理误分类误差的程度却鲜为人知。我们估计了加拿大新斯科舍省邮政编码地理编码以分配人口普查地理区域时的误分类误差。
我们在两个普查行政区级别（即传播区域（DAs）和普查分区（CSDs））检查了新斯科舍省邮政编码地理编码的计数与建筑物实际位置的匹配率之间的差异。实际位置基于省政府收集的包含建筑物实际纬度/经度的数据。还使用加拿大统计局的分类评估了按农村程度划分的误分类差异。
在两个城市地区（哈利法克斯都会区和悉尼）之外，计数差异小于10%，许多传播区域的差异大于30%。匹配率呈现出类似的模式，绝大多数非城市传播区域的匹配率小于40%。即使在主要城市地区，10%的传播区域也存在较大的误分类误差。在普查分区级别上，如果不进行进一步的区域汇总，误分类误差仍然太大，无法估计计数或比率。
应使用公民地址或经纬度等附加标识符对位置信息进行地理编码，取代邮政编码地理编码的常规使用。如果数据持有者在向研究人员提供数据之前在内部进行此操作，那么在保护机密性的同时，地理分析的准确性和能力将得到提高。
