NHS Data Migration Subpack : Mapping Tables from Read v2/CTV3 to SNOMED

Closed 18 Oct 2019

Opened 13 Sep 2019


Both Read v2 and CTV3 are now deprecated and static standards; there will be no changes to either of these terminologies. Mapping tables from these deprecated standards to SNOMED were first published in 2007 (rctsctmap) and 2009 (ctv3sctmap). Major quality assurance programmes of the content were carried out during 2010, 2016 and 2017, in collaboration with a sub-group of the Joint GP IT Committee. They are used by Summary Care Record, QOF, GPES, GP2GP and other national programmes. This national use continues to result in requests for small numbers of changes to the maps.


Since April 2017, the majority of all changes occurring to the mapping tables have been largely restricted to fully automated maintenance: where a Read v2 or CTV3 code has a map to a SNOMED code that is now inactive, an active substitute is identified and the next published version of the map is updated accordingly. Identifying the correct active map substitute uses the NHS History Substitutions table, a terminology product published separately by NHS Digital and a recommended component of all implementations required to process inactive SNOMED codes.


Within GP systems today, an increasing volume of SNOMED codes now entering GP records have been directly selected from SNOMED rather than arrived at by mapping from READ. This includes growing volumes of coded data received from external systems, including Secondary Care. As with the narrower set of SNOMED codes to be found specifically in any particular version of the mapping tables, we should expect that some of these codes will also eventually be made inactive in SNOMED. For this reason, all systems expecting to process SNOMED codes derived from such GP systems should therefore be able to manage inactive codes in SNOMED CT.


Given that systems must already independently manage inactive SNOMED codes, and that the technique for managing them is the same whether the inactive codes came from mapping tables or were directly selected, NHS Digital believes there is no longer a requirement or benefit from continuing to centrally manage the issue of SNOMED code inactivity specifically in the Mapping Tables.

 NHS Digital’s current intent is therefore to continue to make the current mapping tables available but as static data artefacts; they will not be routinely updated after April 2020. If individuals rely on the mapping tables to manage inactive codes, then other issues will increasingly arise through not correctly managing inactive SNOMED codes elsewhere in the system. As previously stated, we know that such codes already exist in GP records.

Why your views matter

Documentation for the mapping tables has always stated that updates would stop from April 2020, and this remains the intention. This consultation is to provide the opportunity for external users to highlight any issues this might raise for their particular use.

We will use the feedback to understand any perceived issues that users of the mapping tables might have if they are no longer updated after April 2020. This might result in further educational materials or training on how to manage inactive codes in SNOMED CT.


  • All Areas


  • TRUD SNOMED CT Subscribers


  • Read Codes