Data Linkage

HDNS datasets are linkable to each other and to external datasets, where approved by the HDNS Data Access Committee and the custodian of external datasets.

What is linkage?

Linkage allows information on an individual from one data source to be linked to information on the same individual from another data source. Using the linked data makes it possible to gain a more comprehensive understanding than could be obtained from either data source individually.

Linkage can also be used for conducting longitudinal analyses within the same data source, even when identifying information is recorded inconsistently, incompletely or has changed over time.

The approach to data linkage outlined on these pages allows for security and consistency in the linking of data across multiple data sets, disciplinary areas, time periods and projects, resulting in a high-quality research product.

Linking External Datasets

Linkage of external data sets with HDNS data must be approved by the HDNS Data Access Committee.
External datasets are data that are not currently part of HDNS’s holdings, for example: (i) data from a clinical trial, research study or survey; (ii) data from patient registries including disease or population–based data; or (iii) data from other organizations or custodians. 

When preparing a dataset to send to HDNS:

  • Ensure that all direct identifiers such as names and street addresses are removed. Double check ‘free comments’ fields or other fields to ensure there is no potential identifying information included. 
  • Follow the process for encryption of common identifiers such as HCNs, provider numbers and SINs provided by HDNS.
  • Confirm that you are only sending the variables for importing that have been approved by HDNS.
  • Only use a secure file transfer method approved by HDNS.

For more informaion please review our Guidelines for Data Linkages [PDF - 163kB] or contact HDNS at