In the January 2019 issue of Standard Practices, we explored the application of different device classification schemas to support different purposes, from spend analysis to device risk assessment. Recently, the Device Categorization Work Group of the AHRMM Learning UDI Community (LUC) published its report on the relationship between the two classification systems linked to the U.S. Food and Drug Administration (FDA) Global UDI Database (GUDID). Those systems are:
- The Global Medical Device Nomenclature (GMDN)
- The Systematized Nomenclature of Medicine – Clinical Terms (SNOMED CT)
A GMDN term is designed to reflect approved use of a product, although many manufacturers use it to designate approved use by regulatory jurisdiction. As a result, the same device could be assigned different terms across different regulatory jurisdictions.
SNOMED CT uses “concepts” that are identified by a code and refer to a name and description. For example, the code for a cardiac pacemaker device would include the semantic tag “physical object” to distinguish it from the code for a procedure in which such a device is used.
The culmination of a two-year work effort, the report warrants another exploration of the potential opportunities (and challenges) associated with linking two systems that originated for different purposes. As the report states, “GMDN is used to classify devices within the GUDID for regulatory purposes,” while SNOMED CT’s principal use has been to “encode clinical information (e.g., diseases, findings, procedures)” in a variety of information technology, including electronic health records (EHRs) and clinical registries.
The GMDN term is a mandatory field in the GUDID. The GMDN term code, or SNOMED CT code, is required to document use of implantable devices in EHRs as part of the Centers for Medicare and Medicaid Services (CMS) Promoting Interoperability program (formerly Meaningful Use of EHR Incentive program). Proper use of SNOMED CT for quality reporting is also required to optimize reimbursement under CMS’s Merit-based Incentive Payment System (MIPS). The report notes that SNOMED CT has well-defined file formats for sharing codes and related data and encourages inclusion of UDI device identifiers (UDI-DIs).
What does SNOMED CT have to do with medical devices?
While SNOMED CT is well known as a clinical terminology, many do not realize it also covers other domains, including drugs and devices. GMDN is used as the basis for medical devices in SNOMED CT, as the result of a 2012 agreement between GMDN Agency and SNOMED International, the two organizations that manage the data and code sets, respectively. Currently, 9,000 GMDN terms for clinically-significant devices, e.g., implants, are part of SNOMED CT. A table that maps one specific GMDN code to one specific SNOMED CT code supports the linkage between the two coding systems and the UDI-DI. By linking to the UDI-DI, the codes could more easily be associated with other device attributes in the GUDID and other sources.
As the LUC report describes, categorizing devices and related information in this manner provides greater insights into devices beyond simple identification. GMDN provides a classification system according to intended use, while SNOMED CT enables coding appropriate for EHRs and registries to study what devices are used in what kinds of procedures. By linking to the exact device and associated attributes, researchers can glean more precise data about the performance of not only specific devices but also specific attributes for particular patient populations. In other words, it is the relationship between the various data elements (device identifier, intended and actual use, and device attributes) that provide deeper insights to support both product innovation and patient safety.
Both GMDN and SNOMED CT offer free use of their data sets. SNOMED CT use is free in the 34 countries that are members (as well as in low-income countries), while GMDN began offering a free membership in April 2019. Today, approximately 90 regulatory agencies and 4,500 medical device manufacturers are registered to use the GMDN system.
The report did identify challenges as a result of the two systems having different data structures. For example, it is hard to maintain the one-to-one mapping table when there are changes made to GMDN terms. A GMDN term can be expanded (from a “knee arthroplasty force sensor” to an “arthroplasty force sensor”) or narrowed (from an “ENT foreign body extractor” to an ENT foreign body inflatable extractor). On the other hand, SNOMED CT must create new codes vs. changing existing ones, in order to protect the consistency of its codes to support longitudinal research.
The work group also referenced the value of other classification systems, more familiar to supply chain professionals, such as the United Nations Standard Products and Services Code (UNSPSC) and the Universal Medical Device Nomenclature System (UMDNS). When it comes to classification systems, it is not about either/or but rather both/and. The use of different systems, and the ability to create relationships between them, provide richer views into the products used in healthcare, and allow us to better perform a variety of tasks, from spend analysis and inventory control to the generation of real world evidence about product use and performance.
