The art and science of record linkage: methods that work with few identifiers

Increasing use of administrative records for research purposes has led to the need to develop methods for linking records. Linkage of the data from the Manitoba Health Services Commission (MHSC) with Canadian Vital Statistics records was done to verify Manitoba deaths, to measure degree of agreement between the two data sets, and to link "cause of death" information from Vital Statistics back to medical histories. A multi-stage approach to matching was adopted. Individual records matching perfectly across a number of relevant variables in the two files were selected first, reducing the number of records going through the probability matching to manageable proportions. Overall, almost 96% of the MHSC records were well matched with Vital Statistics records. Both uses of the matched data and various ways to confirm data quality are discussed.