We have been made aware of a limitation with the CPRD Aurum code browser.
Background
To address the issue of a significant number of irrelevant (veterinary) SNOMED codes being added to the CPRD Aurum medical dictionary, from November 2021 CPRD changed the way the dictionaries were processed by only including codes which appeared in the CPRD Aurum data for the corresponding monthly view. However, we have become aware that EMIS retire and replace codes intermittently. This means that retired/replaced codes with >=1 event recorded in an earlier build, could have fewer or no events recorded in a subsequent build; codes with no events would not feature in the newly generated medical dictionary. This issue also appears to affect the CPRD Aurum product dictionary.
Therefore, the CPRD Aurum code browser is only relevant to the corresponding build (e.g. if you using the CPRD Aurum May 2022 release, you need to use the May 2022 CPRD Aurum code browsers to ensure you capture all relevant events).
This has two implications for researchers using CPRD Aurum data:
- If you use old code lists on a later release, you may miss events recorded with newer codes. This can be addressed by following existing advice to use search strategies to update code lists if these are to be applied to a newer release.
- If you use newer code lists on an older build, you would miss events recorded using retired/replaced codes which do not appear in the more recent release but which were present in the older build. An initial investigation suggests that only a small proportion of codes (~0.16%) decreased by >=20% in the number of events recorded. The majority of these codes relate to vaccinations.
Please note, the CPRD GOLD code browsers are not impacted by this as they are cumulative, containing codes which appear in current and previous builds.
Recommendations
We are working to rectify this issue so that the CPRD Aurum code browsers are also cumulative, containing codes which appear in current and previous builds.
In the meantime, we would advise the following:
- Please use the version of the CPRD Aurum code browser which corresponds to the release you are using for your study (i.e. if you are using the CPRD Aurum September 2023 build, please use the September 2023 version of the browsers). If you need to access browsers from earlier builds please request these by emailing CPRD Enquiries (enquiries@cprd.com).
- Please continue to use reusable search strategies for code list generation and maintenance.
- As the browsers on the online portal are always updated to reflect the latest release, when importing codes into the code browser on the online portal, please double check that all codes have been imported successfully before copying them into the Define tool. There may be instances where you have to manually type the medical/product codes into Define (if they do not appear in the latest browsers) to ensure that all revenant events/patients are captured. However, our investigations suggest that this would be a limited occurrence.
We apologise for any inconvenience this may have caused. If you have any questions, please do not hesitate to contact us.