IPS Terminology User Guide

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SNOMED International HL7 IPS Free Set

In 2019, SNOMED International and Health Level Seven International (HL7) announced the formalization of a license agreement in which a relevant "Free for Use" Set of SNOMED CT coded concepts will be used within the HL7 International Patient Summary (HL7 IPS). HL7 is a not-for-profit, ANSI-accredited standards developing organization dedicated to providing a comprehensive framework and related standards for the exchange, integration, sharing, and retrieval of electronic health information that supports clinical practice and the management, delivery, and evaluation of health services. The HL7 IPS is a minimal and non-exhaustive patient summary dataset, specialty-agnostic, condition-independent, but readily usable by clinicians for the cross-border unscheduled care of a patient. The collaboration is consistent with the aims of both organizations to support international harmonization. 

The SNOMED CT International Patient Summary (IPS) is international in scope and in addition to harmonization with HL7 IPS, is aligned with CEN's European Standard for the Patient Summary. The IPS free set consists of more than 8,000 SNOMED CT terms for use in implementations of the HL7 CDA R2 and FHIR IPS Implementation Guides worldwide. The SNOMED CT IPS free set contains concepts that can record the following data:

  • General information about the patient (e.g., gender)
  • Medical summary of most important clinical data (e.g., allergies, current medical problems, major surgical procedures)
  • A list of current medications

The IPS Free Set is available for non-Member Affiliates as a plain list of concepts and their descriptions, supporting the use case of data exchange, but lacking all the capabilities provided by the SNOMED CT ontology, available only to members in complete SNOMED CT relaeses.

The SNOMED CT IPS RF2 refset is available from SNOMED International and is maintained and updated annually, in line with the latest SNOMED CT International Release.

Access within SNOMED International member countries is provided by the Member National Release Centre in each country, via the relevant Member page. Affiliates of SNOMED International in non-member countries can access the refset through their Member Licensing and Distribution SERVICE (MLDS) account. Please contact info@snomed.org for more information if required.

SNOMED International IPS Terminology

The SNOMED International IPS Terminology represents an evolution of the IPS Free Set, adding the relationships that transform this content into a sub-ontology of SNOMED CT.  A sub-ontology is a functional set of concepts and relationships extracted from the full SNOMED CT Ontology, providing new features:

  • It can be loaded in a SNOMED CT compatible terminology server
  • The content is organized into the same hierarchies present in the complete SNOMED CT Edition (i.e. Clinical Findings, Procedures, etc)
  • The content is expanded to include a small set of additional grouper concepts, the minimum necessary to construct the SNOMED CT hierarchy structures
  • It's possible to run ECL (Expression Constraint Language) queries over IPS Terminology content to support terminology binding and data analytics
  • All these features are limited to the reduced content in the IPS Terminology, compared to the full release of SNOMED CT 

The IPS Terminology is available as an RF2 package, with a similar format to any SNOMED CT Edition package. The content is only available in "snapshot" format (including only the last state of each component), and it only includes active components at the moment of the terminology extraction. The package does not include historical information, which is available to licensed affiliates in the full SNOMED CT release.

The RF2 package of the IPS Terminology can be loaded into any compatible terminology server and can be navigated with terminology browsers. SNOMED International provides a browser for the IPS Terminology in: https://iaa.snomed.tools/?perspective=full&conceptId1=138875005&edition=MAIN/SNOMEDCT-IPS-TEST2&release=&languages=en

Example of use

The HL7 FHIR IPS Implementation guide specifies the terminology binding for each of the IPS components, for example, the "Procedures" value set (http://hl7.org/fhir/uv/ips/ValueSet-procedures-uv-ips.html), that defines the valid codes for the "Procedures" resource in the IPS composition (http://hl7.org/fhir/uv/ips/StructureDefinition-Procedure-uv-ips.html), specifies a logical definition with inclusion and exclusion clauses as follows:

Using the IPS Terminology installed in a terminology server it's possible to create an ECL expression that is equivalent to this FHIR logical definition in order to support the extraction of the exact list of concepts that are included in this value set:

This ECL expression can be submitted to a terminology server through its API and the IPS Terminology content will be filtered for this specific use case, identifying a procedure, returning only the valid concepts for this purpose. It was not possible to perform these constraint operations with the IPS Free Set, it has been enabled by the sub-ontology structure and features. 

The ECL Expressions also facilitate updating to new releases of the IPS Terminology or to adopting a complete release of SNOMED CT, and the resulting set will be computed in real time from the available content.


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