NB-IRDT does not receive Medicare numbers and so is unable to do its own data linkage. The Institute has adopted, in partnership with the New Brunswick Department of Health (DH), a process of crosswalk file creation by DH.
To create a crosswalk file, data custodians are required to assign an interim record ID to each records selected for transfer. Prior to transfer, the data set is vertically divided into two parts, a program file that contains only the interim record ID and variables of research interest and a source ID file containing only the interim record ID and identification variables such as name, address and birth date that are available in the medicare registry database of DH, and send the program files to NB-IRDT and the source ID file to DH. Upon receiving the source ID file, the Department of Health attaches a unique Institute ID to every interim ID by joining on the identification variables, creating a crosswalk file that contains Institute ID and the interim ID only and sends the crosswalk file to NB-IRDT. When both the program file and the crosswalk file are received, NB-IRDT replaces the interim ID in the program file by its corresponding Institute ID in the crosswalk file.
The Institute ID is universal and makes data from different providers linkage. For an approved project, the Institute IDs across the project data sets are scrambled into a project-specific unique identifier IDs. On its own the Institute ID does not convey any identifiable information, nor can it be reverse engineered to determine an underlying Medicare number. However, since the Institute ID is what makes data sets linkable, specific safeguards applied to this process include non-disclosure by DH of how Institute IDs are assigned, the complete deletion of all crosswalk files by DH thirty days after transfer to NB-IRDT, limited staff and access permission for creation of project folders, and the replacement of the Institute ID with a randomly scrambled number prior to access by researchers.
