IJPDS International Journal of Population Data Science

Patients use different health services for different reasons, and the details of each visit are documented electronically. There is increasing interest in the use of these real-world health data for public health and clinical studies. To maximise the research potential of these electronic health records, the linkage of data from different settings, such as GP practices and hospitals, creates a more complete picture of a patient’s healthcare journey.

The National Health Service (NHS) England has changed their approach to linking patient records from GP practices to hospital data. A new paper published in the International Journal of Population Data Science (IJPDS) describes the linkage method (via the Master Person Service) and what it means for researchers using anonymised, electronic health data collected by the Clinical Practice Research Datalink (CPRD).

CPRD is a UK Government research service that supports public health and clinical studies.  CPRD data are used worldwide, by regulators, academic researchers, and the life science industry who can request access to patient-level primary care and linked secondary care data for approved research studies.  NHS England links records on behalf of CPRD. The new method was applied for the first time to link CPRD data in November 2024 and there is a need to understand the impact on research for researchers who use CPRD data.

The findings of the paper highlight some advantages of the Master Person Service linkage method. Compared to the previous method, it provides complete coverage of all patients who have interacted with an NHS service, thereby increasing the chance of successfully linking a person’s primary care record to their secondary care data.

The outcome of the matching process also helps researchers distinguish between people who could not be linked to any hospital data and those who were never admitted to hospital. “This information is particularly beneficial during the study preparation stage,” said lead author Justin Chan. “Researchers can more appropriately prepare their study data and remove data from people who were not able to be matched to the datasets of interest.”

The study illustrates the benefits of the new linkage method. CPRD plans to conduct more investigations to examine the linkage method with a view to supporting researchers to prepare and produce better quality research.

 

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Justin Chan, Researcher, Clinical Practice Research Datalink (CPRD), Medicines and Healthcare products Regulatory Agency (MHRA), London, United Kingdom

Chan, J., Barnett, R., Hodgson, S., Chohan, P., Mantovani, G. and Campbell, J. (2026) “Linking primary care data from Clinical Practice Research Datalink to secondary care and other health-related patient data: update and implications”, International Journal of Population Data Science, 11(1). doi: 10.23889/ijpds.v11i1.3069.