Non-standard linkage service

CPRD has a number of standard linkages with other datasets and the full list of currently available linked data can be found on the CPRD linked data web page.  

If a dataset is not already linked to CPRD primary care data as standard, CPRD can be commissioned to undertake a non-standard linkage. Researchers wishing to use the CPRD non-standard linkage service should submit a completed Non-Standard Linkage Service Application Form after reading the associated guidance. If they have any questions about completing the form they should contact the CPRD linkage mailbox


Applicants can contact to request a CPRD model data flow diagram template created in Visio 

What is the process for requesting a non-standard linkage?

The process for obtaining a non-standard linkage is outlined below with some indicative timings and costs which will vary depending on the details of the specific linkage.  Overall costs will depend on CPRD time for the linkage process, standard CPRD charges for data extraction and provision, and pass through costs from third-parties, for example the NHS Digital DARS application fee.  

Stage Process Timings  Cost 
Stage 1A: Initial assessment

Applicants need to read the Non-Standard Linkage Service (NSLS) Application Form Guidance and complete and submit the following to the CPRD linkage mailbox (   

  • The Non-Standard Linkage Service (NSLS) Application Form with any required supporting evidence, e.g. a data flow diagram 
  • The New Client Request Form if the Applicant has not previously used CPRD data. 

CPRD will conduct an initial assessment of the NSLS Application Form (and the New Client Request Form if required) within one month, and inform the Applicant whether: 

  • The New Client Request Form has been approved 
  • The application form can be passed forward for to stage 1B for a detailed assessment.  

A non-refundable initial fee of £1,500 will be payable to CPRD for the processing of the application in Stage 1B and that CPRD will not commence stage 1B of the Non-Standard Linkage Service process until the full fee has been received by CPRD.   

1 month Free
Stage 1B: Detailed assessment

CPRD will review the NSLS Application form to establish whether the linkage is viable based on a number of factors (i.e.  patient confidentiality, legal and technical feasibility, timescale, determining which approvals are required, etc.) and will then inform the Applicant whether the proposed linkage can be taken forward to the next stage. 

If the Applicant confirms that they wish to progress to Stage 2, a contract with CPRD will need to be signed, including a non-refundable service fee.  

2 months £1,500
Stage 2: ISAC, CAG, additional approvals including DARS applications

Example 1: Individual patient-level linkage based on patient-level identifiers: 

CPRD will work with the applicant to: 

  • Prepare, issue and sign a contract for the linkage process 
  • Review information governance-related aspects of an ISAC application prior to submission  
  • Apply for any other required approvals (e.g. HRA CAG or ODR), in collaboration with any other data controllers. 
  • If required open and complete an NHS Digital Data Access Request Service (DARS) application, in collaboration with the applicant and any other data controllers. 

- CPRD will submit the DARS application to NHS Digital only once all other approvals are in place (e.g. ISAC, HRA CAG etc). 
- The NHS Digital DARS team will pre-review the DARS application and once this pre-review is complete, will present the application to the NHS Digital Independent Group Advising on the Release of Data (IGARD).  
- IGARD approval may require several resubmissions. CPRD will undertake one resubmission to IGARD as standard, further resubmissions may incur an additional service charges depending on the work needed.  

Once all approvals are in place, CPRD will: 

  • Prepare a Data Sharing Agreement (DSA) with any third-party data controllers. 
  • Prepare a Dataset Agreement with the applicant
13 months £10,500

Example 2: Non-standard linkage based on GP practice postcode (including release of the linked dataset) 

The process will be as above but potentially requiring fewer approvals (i.e. potentially excluding HRA CAG and the NHS Digital Data Access Request Service (DARS) application) but including the data linkage and release process below (stage 3).

6 months £6,800
Stage 3: Data linkage and data release

Depending on Data Flows agreed between the applicant, any third-party data controllers and CPRD, the linkage will be undertaken by either NHS Digital or CPRD. For most non-standard linkages this process involves: 

  • NHS Digital producing a bridging file to enable linkage of pseudonymised/de-identified datasets and sends this to CPRD 
  • Any third-party data controllers provide CPRD with study relevant patient IDs and variables 
  • CPRD then creates new linked dataset using the bridging file, CPRD data and the third-party data controllers provided data.  This includes re-pseudonymising all IDs to a study specific ID. 

CPRD, on behalf of the third-party data controllers, manages data releases to the applicant i.e. signing of the Dataset Agreement and secure transfer.

2 months £9,300
Total  Example 1: Individual patient-level linkage based on patient-level identifiers  18 months  £21,300
  Example 2: Non-standard linkage based on GP practice postcode  9 months  £8,300

If needed, you can download the new client request form on the Data access web page  

Conditions for a non-standard linkage with CPRD

  • The applicant must provide all information requested on the Non-Standard Linkage Service application form and provide requested information to CPRD in a timely manner.   
  • Non-standard linkages must follow standard CPRD Data Flows which, for patient level linkages must use the CPRD preferred trusted third party (currently, NHS Digital) to carry out linkages on CPRD’s behalf. 
  • For all non-standard linkages CPRD will create and release the final study dataset which will include study specific pseudonymised identifiers only.   
  • Currently, individual patient-level linkages can only be carried out for health and standard health-related datasets. 
  • The applicant must have provided formal approval in principle for the linkage from all third-party data controllers required for the linkage.   
    - While CPRD does not require a specific format for this approval it must follow the principles outlined in the Non-Standard Linkage Service Application Form Guidance. 
  • CPRD will undertake the linkage under its own HRA-CAG Section 251 approval and acts as the lead applicant on the NHS Digital DARS application.
[Page last reviewed 30 November 2018]