Why do we use Reference Sets?
What are Reference Sets?
Reference Sets (or refsets) are collections of codes which have been arranged into groups to represent a general condition or an event. Also known as Code Clusters, they help to identify similar codes.
The refsets for primary care are curated centrally by the NHS, and can be searched by end users on the Primary Care Domain reference set portal.
The filters on the PCD refset portal can show:
- which codes are in a cluster
- which clusters a code appears in
- which indicators a cluster is used in
Why do we use Reference Sets?
Reference sets have a huge advantage when building searches for internal use, national reporting, and even research. They allow searches to be constructed quickly and concisely so that everybody with (or without) a particular condition or type of code can be counted. Refsets offer longevity because the list of codes will be automatically updated whenever codes are added to the cluster; previously a search showing codes was only accurate at the point it was created.
In both EMIS Web and TPP SystmOne, refsets are used in searches and reports to ensure a standardised set of codes are used.
In EMIS Web, refsets allow searches to run much faster than lists of codes.
How Reference Sets appear in the clinical system
Both EMIS and TPP regularly update refsets by updating their code dictionaries from the monthly TRUD release.
EMIS Web
In EMIS Web we see an 18 digit number in place of clinical codes. There is unfortunately no way of knowing at a glance what this number represents, but it is possible to double click the number which brings up a list of the SNOMED codes contained within it. The conclusive way of knowing what refset it is would be to take a note of the number and look for it within the PCD reference set portal using the Refset ID filter.
In EMIS Web, DM_COD usually appears as part of DM_DAT, which also tests DMRES_COD to check whether a patient has a diabetes resolved code.
TPP SystmOne
SystmOne uses Cluster IDs for the end user which can be easier to understand. It would still be necessary to Amend or Copy the search to see the logic, but here it is possible to see the cluster which might show as DM_COD.
When searching for refsets to use, SystmOne helpfully lists them in alphabetical order but there is still a catch. Many refsets which are used by a particular service have been given a prefix which again can be helpful to see all related refsets listed together. It also means that there can be an fair degree of duplication. Take for example the immunocompromised cluster IMATRISK1; this appears several times as C19IMATRISK1, FLUIMATRISK1, PPVIMATRISK1, SHIMATRISK1.
Changes
Occasionally a refset is updated, meaning that new codes might be added. Codes are rarely removed from a refset, although it does happen if it has been identified that a code was accidentally included. Codes that have been marked inactive (ie: the end user is no longer able to find and add a particular code to a record) remain in a refset since it is often important to ensure that historical entries are picked up.
The advantage to searches and reports is that they can remain current without the need to deploy new versions. A example comes from the CAN_COD refset which in 2022 saw hundreds of new cancer codes added to the cluster. These weren't newly discovered cancers, but the result of creating SNOMED concepts for very specific subtypes
If NHS Digital decides that there need to be similar but not identical refsets we will often see the cluster ID given a number. CKDATRISK1 only looks for CKD stage 4 and 5 codes, while CKDATRISK2 looks for stages 3-4-5. Two clusters for chronic respiratory disease CRDATRISK1 and CRDATRISK2 have a huge degree of overlap and each contains a similar number of codes; however CRDATRISK1 is only used for the Pneumo Enhanced Service as an at-risk group, while CRDATRISK2 is used by the Flu Enhanced Service for its at-risk groups!
This can become very confusing to patients and Practice staff if a patient happens to have one of the codes which only appears in one group. Why should they be eligible to receive a flu jab but not pneumo, or vice versa? Of course, both Enhanced Services have a provision for the Practice to code that the patient has been clinically assessed that they Need a flu/pneumo vaccination to ensure activity payment. The challenge is often identifying where these gaps lie, but this is where Primary Care IT provides a number of eligibility checking protocols as well as the CQRS searches to help pick up recent activity which will not be funded unless coding action is taken.
Missing codes
There have been some events following code dictionary updates where codes have been accidentally removed from a cluster. Some basic checks before reporting to EMIS or TPP may help.
- Check the cluster (double click a cluster ID in EMIS Web, or use the Read Code Browser in SystmOne)
- Check the PCD refset portal - has the code been removed?
- Are other Practices seeing the same problem?
EMIS had a recent event where a drug had been removed from a code cluster following the MKB203 update. It was possible to confirm from another site that the drug was still included in MKB202.
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