By Kelly Kuru, Chief Communications & Collaborations Officer, SNOMED International.
In a recent podcast, I spoke to Marjorie Rallins, Executive Director, Health Data Standards at LOINC (logical observations, identifiers, names and codes). We discussed our ongoing collaboration between the two organizations and the recent release of the LOINC Ontology, focusing on what it includes, how it supports implementers, and how it will be updated and maintained. It’s an exciting development that both organizations have been working hard at and we know will really help both of our stakeholder communities – and, ultimately, patients and care providers.
LOINC, as Marjorie explains in the podcast, is an international standard for representing clinical observations and measurements. It initially emerged in 1994 as the project of a researcher at the Regenstrief Institute who identified the need for a standard to share clinical documents electronically. It is published in February and August each year.
SNOMED CT, a robust clinical terminology with more than 350,000 concepts, is also a health data standard used in more than 80 countries worldwide.
So what is the LOINC Ontology? An extension of SNOMED CT’s ontological framework that creates SNOMED CT and LOINC codes for all concepts shared between the terminologies, the Ontology grew out of a collaboration both organizations signed in 2022 to work together for the good of all our users. In late 2024, we released a technical preview of the Ontology with the goal of seeking feedback from our user communities as we continued to build it out. Essentially, LOINC content is represented in the Ontology using SNOMED CT's concept model.
We – a team of about 10-12 people – co-developed it because both organizations have long understood that providing a single solution makes it much easier for those who implement different combinations of the two standards in health information systems. I should add that the relationship between the two organizations goes back at least two decades at this point, if not longer, so we had a really strong foundation to build upon. Marjorie, calling the endeavour a “labour of love,” says she sees the two organizations and their respective stakeholder communities as overlapping on a Venn diagram.
Our (SNOMED International’s) contribution is the SNOMED CT computable framework; LOINC provides laboratory and pathology content in an understood format to countries that do not currently use LOINC. Both our organizations are highly engaged with our members, who guide us and help us understand what they need.
“After about 10 years, we said, ‘Let's figure this out,’ says Marjorie. “And we did.”
The Ontology is also well-aligned with the interoperability-related work happening in the European Health Data Space, which is currently establishing a common framework for the use and exchange of electronic health data across the European Union.
What’s inside
The March 25 Ontology production release features more than 35,000 concepts, including quantitative lab tests and the top 200 most used lab tests ordered. This initial release includes concepts that represent at least 80% of test volume; it focuses on the most frequently used terms as defined by LOINC’s Top 20,000 rankings.
In the future, you can expect to see the incremental addition of the domains of information (lab, clinical, documents, radiology, survey instruments). Eventually, the plan is to have all of the content that should be integrated into the extension represented for use as well. It might take us a while to get there, but we’re committed to moving in that direction!
To accompany and support the Ontology, both organizations have collaborated on producing the Implementation Guide for the LOINC Ontology which provides detailed instructions and strategies for leveraging the extension, with the goal of enhancing interoperability and facilitating global health data exchange. The guide covers the creation of SNOMED CT concepts for LOINC terms, reducing duplication and fostering collaborative efforts, and helps users understand how to implement both LOINC and SNOMED CT standards, enabling them to meet clinical and regulatory requirements efficiently.
It also offers a number of clinical use cases and their corresponding benefits. Those use cases include ordering lab tests; standardizing lab test results from SNOMED CT to LOINC; cross-terminology navigation, querying and retrieval of laboratory data; standardized reporting of laboratory procedures and observations; integration of Clinical Decision Support Systems for laboratory data; facilitation of interoperable health information exchange for laboratory results; follow-ups; financial logic; and efficient searching.
We’re really looking forward to getting feedback from users and to understanding how it can or is being used for purposes beyond clinical, such as analytics. Marjorie gave a great example in the podcast of how the Ontology could be used for analytics: Say a LOINC user needs to understand which hospital patients develop a post-operative infection. Before the availability of the Ontology, that user would have to use LOINC for the lab data and, separately, SNOMED CT to identify those patients. Now, with a single solution, their work is much less complicated.
If you are interested in learning more, check out our podcast. You can also view the recording of the March 24, 2025 LOINC Ontology webinar on the LOINC Ontology website. Read the official press release here, and download the LOINC Ontology here.
We look forward to hearing from you throughout the process and to learning about your individual use cases.