Data Linkage Research

What is data linkage?

In England the NHS records information about patients whenever they attend their GP or are seen/admitted to hospitals. Civil registration data (births and deaths) is recorded by the Office for National Statistics and is available to the NHS. This information is stored in various different databases controlled by a wide variety of NHS healthcare providers. Similar systems are in place in Wales, Northern Ireland and Scotland.

When we undertake research studies we usually need to find out what happens to those people participating in research after they have entered the research study. The conventional way to do this is for a member of the research team to see or contact the research participant to directly gather further information. This is quite expensive to do, particularly for very large research projects that run over a long time period.

Because the NHS records and stores information about people in electronic databases, researchers can ask for approval to access this information as an alternative to getting the information directly from research participants. Care has to be taken when doing this to make sure peoples' personal information is protected and not used without their permission.

To be able to access electronic healthcare data to add to a research study, or just to join two different databases together, we have to link the electronic data. This is what we mean by 'data linkage'. In healthcare research we commonly use NHS numbers for this. Because NHS numbers are unique to any one person if we have two databases that contain NHS numbers we can link the information for each individual from one database with the information from another database.  

We have been using electronic healthcare data made available from NHS Digital (the NHS data 'warehouse') in our current research and plan to use this approach in the future. More details of what we do and how we protect peoples' personal information is given in the research project descriptions below. We are particularly interested in obtaining feedback on our proposed future projects to help us make sure our approaches are publically acceptable.


Current research using data linkage:

The UK Aneurysm Growth Study (see 'Why and how do we access your electronic health records?")

Data linkage in the NHS AAA Screening Programme


Future research in which we are planning to use data linkage:

Virtual Aneurysm Screening Study

Double-screening: A randomized trial of screening for peripheral arterial disease at the same time as AAA.

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