Data linkage methodology and outcome

Data linkage, also known as data integration, is a process that brings together information relating to an individual from more than one source. This web report utilised probabilistic linkage between three datasets: Defence-held Personnel Management Key System (PMKeyS) data, Department of Veterans’ Affairs (DVA) Clients data set and the Medicare Benefits Schedule (MBS) and Pharmaceutical Benefits Scheme (PBS) – including Repatriation Pharmaceutical benefits Scheme (RPBS) data.

After undergoing data checking and cleaning, the PMKeyS and DVA client data set were linked using a probabilistic data linkage. They were matched by name, sex and date of birth. The linkage procedure involved creating record pairs – one from each data set – by running a series of passes that allow for variation in full name information and demographic data. A manual clerical review was conducted to manually examine the linkage data for proposed match pairs and decided whether to accept or reject the match. There were 47,685 links found in the PMKeyS-DVA linkage, representing 46,927 distinct PMKeyS cohort members (DVA clients), the difference were duplicate records in both datasets. Some links were missed due to postcodes and changed last names. Additional links were identified and verified by inspection which produced a total yield of 47,023 distinct PMKeyS cohort members linked to DVA data.

After linking to the Medicare Enrolments File and applying exclusionary criteria used in previous VHWU analysis, the final PMKeyS dataset had 117,801 ex-serving individuals with one day of service since 2001. The raw PBS/RPBS dataset contained 8,789,463 rows and linked to the PMKeyS cohort with any records no longer linked deleted from the data. The termination date from all PMKeyS individuals was also linked to the PBS/RPBS. The final PBS/RPBS dataset contained 7,027,860 dispensing records from 101,695 distinct individuals.

All data linking was carried out by the Data Linkage Unit at the AIHW – one of only three accredited Commonwealth Integrating Authorities. This accreditation requires the AIHW to adhere to stringent criteria and abide by the National Statistical Service High level principles for data integration involving Commonwealth data for statistical and research purposes and best practice guidelines. As well as operating within these guidelines, data linkage at the AIHW is carried out under the protections of the Privacy Act 1988, and the Australian Institute of Health and Welfare Act 1987 (which carries additional privacy protections for companies and deceased people).

Strict separation of identifiable information and content data is maintained within the Data Linkage Unit in accordance with the AIHW linkage protocols, so that no one person will ever have access to both. Summary results from the linked data set are presented in aggregate format. Personal identifying information is not released and no individual can be identified in any reporting. The linked data set created for this study will be stored securely on site at the AIHW for 7 years.