Facts and Questions

·         What is Data Linkage WA?
·         What does Data Linkage WA do?
·         What is the WADLS?
·         Which data collections are linked?
·         What is core data?
·         What is data linkage?
·         What is a Linkage Key?
·         What is the difference between Data Linkage and WADLS?
·         What is best-practice protocol?
·         Why is data linkage useful?
·         How is Data Linkage WA funded?
·         What is linked data used for?
·         Who can use the data?
·         What has been discovered so far?
·         Why is the WADLS useful?
·         What about privacy?
·         Where to from here?

What is Data Linkage WA?

Data Linkage WA is a group of health information professionals specialising in privacy preserving methods of linkage of health information. The group was formed as a collaboration between the Department of Health WA, the University of Western Australia, Curtin University of Technology, and the Telethon Institute for Child Health Research in 1995. We are located at the Department of Health WA in East Perth. Data Linkage WA now has 18 staff, consisting of Computer Programmers, Linkage Officers, Project Officer, Data Coordinator, Research Fellows, Systems Support Technicians, Data Systems Manager, Senior Consultants and Program Manager.

What does Data Linkage WA do?

Data Linkage WA has 3 primary responsibilities:1/ To create and manage the links within and between the core DoH (WA) data collections and other relevant data collections.2/ To geocode, or add a map location such as Collector's District (CD) or Statistical Local Area (SLA), using address information recorded on health records.3/ To provide linked and geocoded data for health planning, purchasing, evaluation and research.

What is the WADLS?

The WA Data Linkage System (WADLS) creates and stores the links within and between the State's population health data collections. This system of links is augmented through "extra" links to an extensive collection of external research and clinical datasets.The WADLS does not contain any clinical or service data, but consists of groups (or chains) of "links". Each "link" is associated with a particular record in one of the original data sources. All the "links" in a particular "chain" have been associated with the same individual through the process of probabilistic linkage.This method of linkage relies on the availability of similar demographic information (e.g. name, sex, date of birth, address) in each data source. However, during the linkage process only about 5 to 10 percent of the records are viewed for checking of doubtful links by Data Linkage staff.The linkage process depends on access to personal demographic information derived from each of the contributing data sources, but the health details are stored and managed separately.

Which data collections are linked ?

The data collections routinely linked by Data Linkage WA are: midwives notifications, cancer registrations, mental health clients, hospital admissions and emergency presentations. Electoral, birth and death records are linked routinely under a special arrangement with the WA Electoral Commission and the Registry of Births, Deaths and Marriages. Residential aged care records and Medicare enrolments are also linked under a separate Memorandum of Understanding with the Australian Government Department of Health and Ageing.Updates to the links are ongoing and new demographic information is currently received on either a monthly, bi-monthly, quarterly, six monthly or annual basis. This ensures that the links in the WADLS remains as up to date as possible.

What is core data?

We refer to the population health data collections managed within the Department of Health WA as the "core" data. Electoral records and birth, death registrations are also considered to be "core" data for the WADLS.

What is data linkage?

Data linkage is the activity of finding connections between different pieces of information that are thought to belong to the same person, or between events that occurred at the same place or happened at or about the same time.

What is a Linkage Key?

The linkage process generates a set of indexes sometimes called "linkage keys" that are stored by Data Linkage in a Master Links File. These "linkage keys" are held separately from any personal demographic information and they are used to enable related health records to be joined together for approved research projects.

What is the difference between Data Linkage WA and WADLS?

The Data Linkage WA is the organisation that provides linkage, geocoding and client support services to researchers and government agencies.The WADLS is the computer system that allows Data Linkage WA staff to create, store, update, manage and retrieve the linkage keys.

What is best-practice protocol?

The protocol consists of four distinct steps. Firstly, linkage staff create linkage keys using confidential personal demographic information. Secondly, linkage staff extract, then encrypt linkage keys for each particular project. Thirdly, encrypted linkage keys are provided to data custodians so they can add them to their clinical or service details for that particular project. Lastly, researchers receive clinical or service details from each data custodian and use the encrypted keys to connect the details needed for their analysesIn this way access to identifying information is restricted to a specialised linkage team who perform the first and second steps. Data custodians are involved in the third step. Researchers are only involved in the last step.

Why is data linkage useful?

Data linkage adds value to routinely collected data, because the information required to study complex diseases is rarely found in one place. Epidemiologists and population health and health services researchers need to study many factors to make sure their research is meaningful.

How is Data Linkage WA funded?

Funding is provided by the Department of Health WA, the Australian Government Department of Health and Ageing, the University of Western Australia (via NHMRC & ARC grants), Curtin University of Technology and the Telethon Institute of Child Health Research.Costs may be recovered where work falls outside our core activities and this contributes to the on-going development of the data linkage infrastructure.

What is linked data used for?

There are many applications:

• For population based health research and policy development
• To see what might be done i.e. testing hypotheses and pilot studies
• As a capture-recapture tool, to improve the quality of datasets
• For follow-up and comparison of different treatment regimes
• To study the aetiology, comorbidities and outcomes of disease

Who can use the data?

Access to the information is granted to bona fide researchers and planners in WA who meet the stringent requirements of ethics committee clearance. Strict protocols are followed to ensure confidentiality and security of linked data.

What has been discovered so far?

Many research projects have been made possible. Here is just a sample of the results.Infants conceived with the use of intracytoplamic sperm injection or invitro fertilisation have twice the risk of a major birth defect as naturally conceived infants.The annual risk of venous thromboembolism is increased by 12% if one long haul is taken yearly. Airlines and health authorities have been encouraged to continue advising passengers of the risk of DVT.Rates of major physical illness and rate of dying were higher compared to the rest of the population. This work led to the establishment of the HealthRight Advisory group, which made recommendations for changes to the Mental Health Act.Safety and Quality of Surgical Care Project and the Surgical Mortality Audit collaborates with the College of Surgeons to review surgical outcomes and audit any morbidity and death occurring within 30 days following surgery.

Why is the WADLS useful?

It is fair to say that the WADLS holds the "keys" to health and medical research in WA. The "chain of links" design of the WADLS has enabled it to be easily updated and expanded. It now plays an important part in helping many researchers to discover what makes people healthy. It is an extremely valuable research tool for academics, policy planners and analysts.

What about privacy?

Data linkage maximises the use of routinely-collected data, whilst maintaining the privacy and integrity of data sources. One of the reasons the WADLS was created was to ensure the information about individuals is kept confidential. The development and expansion of the WADLS has meant that the use of identified health information has decreased substantially and is continuing to do so. WA research projects using name-identified data fell from 94% in 1994 to 36% in 2003.Any use of linked health information must be approved by an ethics committee, where representatives from the community, the clergy and the law as well as health professionals and researchers review each research application.

Where to from here?

In July 2005, the Minister for Science awarded a two million dollar grant to establish a WA-Based Centre of Excellence in Data Linkage. This will enable significant innovation in the health and human services sector through the creation and sustainable development of infrastructure based on data linkage and population health databases.The best-practice protocol has enabled access to new datasets to be negotiated for linkage to the core system, enabling more questions about health and its determinants to be examined and re-examined.In 2008, there will be an opportunity for WA data linkage stake-holders to be involved in the development of an Australia-wide data linkage capability through the National Collaborative Research Infrastructure Strategy.