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Why is linking health data important?

Record linkage allows a more complete picture of population needs, government service access, health and outcomes than was previously possible. The information can be used to study: 

  • the safety, quality and costs of health care by linking information on different treatments with outcomes such as primary care visits, emergency department visits, admissions to hospital and deaths 

  • the relationships between personal, economic and lifestyle factors and health through linking data from research studies and surveys with outcomes such as emergency department visits, admissions to hospital, cancer notifications and deaths 

  • societal and community influences on health by linking health data with information from other government agencies, such as education and communities and justice services. 

The CHeReL provides advice on the design, cost, feasibility and process of linkage studies. We offer four types of record linkage services: 

  • Linkage between and within records held in the CHeReL’s Master Linkage Key (MLK). 

  • Linkage of other datasets to the MLK.  Often researchers are interested in a particular cohort of people, and want to examine their outcomes or history using routinely collected administrative records.  For example, a cohort of people may be receiving a particular intervention, and the researcher wants to determine the effectiveness of this intervention as measured by later hospital admissions, emergency department presentations and mortality. 

  • Linkage of two or more datasets that are not yet included in the MLK - for example, linkage of educational outcome to child protection data 

  • Deduplication of datasets.  The CHeReL regularly conducts this kind of linkage for data custodians to identify duplicate records within a dataset and records that belong to the same person.  

Biolink

Biolink is a service of the Centre for Health Record Linkage (CHeReL), offered exclusively to clients of the NSW Health Statewide Biobank (NSWHSB). Using state-of-the-art data linkage methodology and expert advice, Biolink enables the biospecimens stored at NSWHSB to be longitudinally linked with a broad range of routinely collected health data about participants. Linkage to routinely collected data provides an efficient and cost-effective alternative to manual follow up of participants’ health service use and outcomes. The Biolink Research Project Manager can be contacted at MOH-Biolink-Cherel@health.nsw.gov.au. 

How record linkage works

Record linkage brings together information that relates to the same individual, family, place or event from different data sources.  In this way it is possible to construct chronological sequences of health and other government service events for individuals.  Combined, these individual 'stories' create a larger story about the service experience, care and outcomes of people in NSW and the ACT.   

An example is a study by a research team who want to investigate whether bowel cancer screening can improve survival.  To address this question the researchers require information about people’s bowel cancer screening from a survey, as well as their cancer incidence, relevant hospital treatment and deaths that are recorded in administrative data collections managed by government agencies. 

Once the relevant government agencies and a human research ethics committee approve the research project, the data can then be securely linked by the CHeReL and made available to the researcher.  

The process by which data is securely linked and made available is as follows:

01

The first step in data linkage is to split the records from each dataset into two separate files. To protect privacy, the identifier information such as names and addresses is separated from the content information, like cancer type or screening history.  The two separate files from each dataset are stored and handled separately. The identifier data is used in the Data Linkage process and the content information without names and addresses is used in Data Integration.

02

CHeReL’s Data Linkage Unit applies a combination of matching methods to the identifier data to identify and distinguish between individuals, e.g. between this John Smith and that John Smith. The identifier data belonging to each individual is then assigned an arbitrary Person Number which replaces the name, address and other identifying details.

03

Using an encrypted version of the arbitrary Person Number, CHeReL’s Data Integration Unit then makes a research Project specific Person Number for each individual (PPN).  A different PPN is created for each research project.  This PPN is then joined to the relevant survey, cancer and hospital data that has been approved for the research project by the relevant government agencies and human research ethics committee.   All records for an individual in any approved project dataset will have the same PPN.  The approved data is released to the researcher, along with conditions on the use of data. 

04

Using the PPN that is attached to the survey, cancer and hospital data, the researcher can combine records for an individual without accessing information about their identity. This helps to ensure that privacy is protected and research in the public interest continues to improve the health system and health outcomes.

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