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Who can receive CPRD data?
Anyone with the relevant funding and approved ISAC application can receive CPRD data from the CPRD@Cambridge team.
Which resources are available to me when using CPRD data?
CPRD is an ongoing live UK-based database of anonymised primary care records. It includes data on demographics, tests, diagnoses, prescriptions, consultations, and more. It does not include genetic data. To obtain a copy of the data dictionary or view a sample dataset, please contact the CPRD@Cambridge team who will be able to assist you. Additionally, other resources such as denominator and lookup files can be accessed via the CPRD Customer Website. For access, please contact CPRD Enquiries at email@example.com.
What does the CPRD dataset look like?
CPRD, unlike many other datasets, is a compilation of several different files and not of one main table or flatfile. There are ten files: Additional, Clinical, Consultation, Immunisation, Patient, Practice, Referral, Staff, Test, and Therapy. The main way to link these files is using the unique patient identifier, however, other identifiers may also be used where appropriate, such as staff ID or consultation ID. The data dictionary and specification files, as well as lookup files will enable you to understand and label each of your variables appropriately once received.
How easy is it to build a flatfile for analysis in CPRD?
Many experienced researchers estimate that building an initial relevant flatfile for analysis constitutes up to 50% of the work of a EHR project. Data management skills are required, but also there are clinical, analytical and conceptual questions about how various variables (e.g. smoking or diabetes) should be defined using the large amount of data available (e.g. one patient may have multiple contradictory datapoints about their smoking status).
Do you have the data on “X”?
The answer to this question will often be yes, if the data are routinely recorded on primary care electronic health records. However, unlike some traditional prospective cohorts, we cannot provide you with a neat single flatfile to examine. Rather, for most studies, you would be required to build your bespoke flatfile yourself from the many files that CPRD provides. This will entail providing a protocol to CPRD, ensuring you have adequate funding, and ensuring you have a team involving relevant topic, analytical, data management and primary care expertise.
Can I get any specific training for the use of CPRD?
There is an online eLearning training course that CPRD provides. In order to gain access, please email CPRD at firstname.lastname@example.org. Some basic training is available within Cambridge for SSC and MPhil students who are using CPRD for their research projects. For more information, please contact the CPRD@Cambridge team.
How long does it take to undertake a project in CPRD?
CPRD audits indicated that the average completed project is published 2.5 years after the initial protocol was submitted. A national school of primary care data advisory group suggested small novel analyses may cost £120,000-£180,000 in staff and data costs to complete. The incremental cost of further studies in the same research area for a team may be substantially lower.
Are there costs associated with data extracts?
The CPRD website notes it is a “governmental, not-for-profit research service” but will have numerous costs associated with gathering, securing and governing data. It is possible to purchase data directly through CPRD or via universities with licenses, who must pass funding on to CPRD in line with their license agreements. To discuss costings please contact the CPRD@Cambridge team.
What is the role of ISAC?
ISAC is the Independent Scientific Advisory Committee to provide scientific advice on research related requests to access CPRD data. They offer peer reviews on the research protocols, highlight ethical or confidentiality issues related to the use of CPRD and provide advice to the Medicines and Healthcare Products Regulatory Agency (MHRA). For more information, please refer to www.cprd.com/ISAC.
Why do I need to submit an application to ISAC?
CPRD is a governmental, not-for-profit research service. It is compulsory for researchers planning a study using CPRD data to submit an application to the ISAC before accessing the data. The ISAC will then advise on the scientific content of the submitted protocol and other specific aspects such as ethical issues. You will not be able to request CPRD data until your protocol has been approved by the ISAC. For more information about the application process, please refer to www.cprd.com/ISAC/isacprocess.asp.
Is it possible for my research protocol to be rejected by the ISAC?
It is rare for a protocol to be outright rejected by the ISAC, unless the applicants have misunderstood the whole concept of CPRD and how it can appropriate be used for research purposes. The main purpose of submitting your ISAC protocol is to help refine the planned research, rather than to filter research protocols as is done by most peer-reviewed journals. Therefore, a more common outcome is to revise and resubmit protocols where they need extra work.
When the ISAC protocol has been approved, what else should I do before requesting the data?
Once you have secured your funding to obtain the data and your ISAC application has been approved, you do not have to do anything else except to inform the CPRD team of your status. One of the fob-holders will then contact you to set up a time to meet to define your population and extract your data. Please note that if your extract is based on one or more conditions (e.g. all patients with a diagnosis of asthma), you will need to build your code lists which will help define your population.
What is a code list?
A code list is in essence a list of medical or product codes. The CPRD@Cambridge team have built up a number of such lists and are aiming to expand the repository of such lists so that they may be shared and used freely across different projects.
How long will it take to receive my data?
From the point that your funding and ISAC application is accepted, a meeting will be set up between yourself and one of the fob-holders to define your population dataset. The data will take approximately two weeks from the point of that meeting to be handed over. Note that your ISAC application may take several weeks prior to this stage to be completed and approved.
How can I get my data?
Depending on the size of your data, the CPRD@Cambridge team can advise you on the best method for handing over data. If you’re in the Department of Public Health and Primary care, a large USB or hard-drive may be best. Otherwise an SFTP transfer may be possible.
What about obtaining linked CPRD data such as Hospital Episode Statistics (HES) or Index of Multiple Deprivation (IMD)?
The CPRD@Cambridge team does not deal with or hand over linked data, except to work with you in defining your patient population for your data extract and download. Once you have this information, you will need to fill out a linkage form sent to you by CPRD and return both that and the list of patient IDs to CPRD. They will contact you in due course to download your data.
Where can I store my data?
You can store your CPRD data in any secure location on your university desktop or laptop computer. If you’re a student (MPhil or SSC), a personal laptop may be used, however, a data sharing agreement contract will have to be signed which includes a statement about deleting the data once the project is over or you’re not longer a part of the University. It is advised that you do not upload CPRD data to a cloud-based storage facility (e.g. Google drive or Dropbox).
Can I request input from the CPRD@Cambridge team on my ISAC application, statistical, clinical, or data management issues?
There is limited input from the CPRD@Cambridge team except to extract and hand over the data for your project. However, if you feel that one or more members of the team are helpful to the progress of your project, we encourage that you informally approach them at an early stage.
What resources will I need to share with the CPRD@Cambridge team?
We encourage everybody who carries out a CPRD-based project to share with us the following documents:
- The finalised and approved ISAC application
- Any medical or product code lists used in the project with a short description of each
- Any (full or part of) Stata do files that may be useful for other projects in the future
- Linkage data you may have received as part of your project
- Your final paper(s)
“Code lists” and bespoke “do files” can be particularly time consuming to locate or develop for your data management phase; so far every project at Cambridge has agreed to share what they have developed and found to permit future projects to develop work at a faster pace. Please label or cite lists so that they can be appropriately cited by future users. Collaborators can utilise information from this repository, and members of the Department of Public Health and Primary Care can access the repository directly.