Standardising Lab Tests and Data using SNOMED CT

Standardising Lab Tests and Data using SNOMED CT

This article shares experiences from a Proof of Concept project that attempted to standardise lab tests of two large regions in Scotland using SNOMED CT. If you are in the UK and want to consider using the NHS England (NHS Digital) standard – Unified Test List (#UTL), then these findings might be useful.

Background – Pathnexus Scotland Pilot

A pilot project was carried out to create a single test catalogue across two large regions (NHS Boards) in Scotland – Grampian and Lothian. Since this is a pilot, the scope is not to cover all test, but needs to cover multiple specialties (blood science, microbiology, immunology)


  • Create a single test catalogue of Lab tests
  • Standardise lab reports: Convert HL V2 + uncoded  HL7 FHIR + SNOMED CT
  • Identify governance process + consensus based review

👉 A quick note – Pathnexus is our flagship product for aligning lab tests and data across multiple sites (or regions), enabling cross-site working and network consolidation

Pathology Interoperability Standards in England

In England, the lab standards mandated for use based on SNOMED CT, HL7 FHIR and UCUM.

  • The UK NRC publish the Unified Test List (UTL)
  • ~4,200 SNOMED CT concepts (mostly results, ~400 requests)
  • So ~3,800 are NEW SNOMED CT concepts for reporting lab tests

What is the Unified Test List? You can read all about the Unified Test List here

Key findings

  • SNOMED CT works quite well for coding lab tests that are used in both primary and secondary care!
  • Works for both requests and results! ✅
  • Works for blood sciences and other domains
  • Mapping existing lab tests to SNOMED CT (or LOINC) needs review and consensus
  • Governance process is key to ensure clinical safety ✅
  • There is missing content in UTL and SNOMED CT as seen in the table below
  • Need for new tests exists across the diagnostics domain
  • This is perhaps where the recently announced LOINC Extension in SNOMED CT might help!
  • Transformation of HL7 V2 uncoded results to HL7 FHIR messages works ✅
Mappings to SNOMED CT – successful and missing content

Applying this approach

You can use the same approach from the Pilot to consolidate your test lists across multiple sites. The generic approach works whether you are doing a network consolidation in England or you are trying to enable cross-site working across multiple sites. Here is a quick video about how you can create a single network wide test list.

Of course doing this in SNOMED CT has advantages which we cover below.


Missing Content – adding new tests

Pathnexus (our lab data harmonisation platform) allows lab specialists to create new tests on the fly. This is how we added new tests that were needed – here are some examples:

  • High sensitivity tests for Troponins I and T
  • Toxic substance tests (toxicology)
  • Enzyme activity measurements

But ask yourself this question: How many monkeypox tests existed before early 2022? The bottom line is that diagnostics is a rapidly evolving field and new tests are always needed. So gaps like this will continue to exist.

The key is not to use `local codes` (or uncoded) tests. Instead, we need a way to create a new test (in less than 2 minutes) that fully describes the new test yet is based on an external standard. That is what Pathnexus enables!

All new tests that we created and users can create with Pathnexus are fully compliant with the SNOMED CT standard. It allows lab specialists to create without being SNOMED CT experts.

Here is a screenshot of some of the tests we created. Notice how they all define the analyte (component), specimen, etc.

New SNOMED CT based that were created for covering gaps in lab tests

Standardisation under the hood

When you use Pathnexus to create a single new test or harmonise your existing test catalogue, it converts your tests into SNOMED CT behind the scenes. Any new test that you create in Pathnexus will be compliant with the SNOMED CT standard. This allows users to achieve compliance with the NHS England pathology standard while you create your network wide single test catalogue.

Our team worked with NHS Digital in the design and development of the UTL standard. We are experts in SNOMED CT (on which the UTL standard is based). We used our expertise to make standards ( SNOMED CT and LOINC) work behind the scenes so lab specialists can focus on being experts in lab medicine.

Post-coordination of Lab Tests

We used on the fly post-coordination to create new lab tests that were needed. Note just because you used post-coordination, does not mean you are stuck forever holding an expression. Pathnexus takes the complexity out of post-coordination. You can save the post-coordinated expression as a SNOMED CT concept and use the identifier.

  • Effective use of post-coordination can allow true lab interoperability – best of both worlds in SNOMED CT and LOINC (LIVD, UCUM, etc)
  • When SNOMED CT releases a new version that is equivalent to the test you created, we can simply adopt that – (all fully compliant with the SNOMED CT standard and technology).

Post-coordination is not complex – Pathnexus allows lab specialists to use it without being SNOMED CT experts.

Where can you learn more about this work?

Does all this sound exciting, then there is a lot more here to unpack and too long for an article. So here are some places where you can find more information:


For those users who are outside of the UK who use LOINC or something like the NPU, here is a brief summary of why the UK chose to standardise lab tests using SNOMED CT.

  • Long history of use of Pathology Bounded Code List (~3,300 Read codes subset – in primary care). So there has never been any usage of pre-existing usage of LOINC.
  • England successfully migrated their primary care systems (from Read) to SNOMED CT ~2018-19, so migrating from PBCL (based on Read) to SNOMED CT for lab data aligns with that vision.
  • Single reference terminology for healthcare in the UK – primary, secondary, community care
  • Can be used in multiple sciences, not just blood sciences – Sarah Harry’s presentation