Promoting interoperability between SNOMED CT and ICD-11: lessons learned from the pilot project mapping between SNOMED CT and the ICD-11 Foundation.

OBJECTIVE: To explore the feasibility and challenges of mapping between SNOMED CT and the ICD-11 Foundation in both directions, SNOMED International and the World Health Organization conducted a pilot mapping project between September 2021 and August 2022. MATERIALS AND METHODS: Phase 1 mapped ICD-11 Foundation entities from the endocrine diseases chapter, excluding malignant neoplasms, to SNOMED CT. In phase 2, SNOMED CT concepts equivalent to those covered by the ICD-11 entities in phase 1 were mapped to the ICD-11 Foundation. The goal was to identify equivalence between an ICD-11 Foundation entity and a SNOMED CT concept. Postcoordination was used for mapping to ICD-11. Each map was done twice independently, the results were compared, and discrepancies were reconciled. RESULTS: In phase 1, 59% of 637 ICD-11 Foundation entities had an exact match in SNOMED CT. In phase 2, 32% of 1893 SNOMED CT concepts had an exact match in the ICD-11 Foundation, and postcoordination added 15% of exact match. Challenges encountered included non-synonymous synonyms, mismatch in granularity, composite conditions, and residual categories. CONCLUSION: This pilot project shed light on the tremendous amount of effort required to create a map between the 2 coding systems and uncovered some common challenges. Future collaborative work between SNOMED International and WHO will likely benefit from its findings. It is recommended that the 2 organizations should clarify goals and use cases of mapping, provide adequate resources, set up a road map, and reconsider their original proposal of incorporating SNOMED CT into the ICD-11 Foundation ontology.

Achieving Logical Equivalence between SNOMED CT and ICD-10-PCS Surgical Procedures.

Surgical procedures are coded in SNOMED CT in the electronic health record and in ICD-10-PCS in administrative systems. We compared the logical definitions of SNOMED CT concepts to the ICD-10-PCS axial components to identify overlap and gaps. The biggest discrepancy was in the surgical approach which was specified in all ICD-10-PCS codes but only in 8.7% of SNOMED CT surgical procedures. Among the top 100 commonly used ICD-10-PCS codes, 25% could be matched fully in meaning and logical definition to pre-coordinated SNOMED CT concepts. Using post-coordination, it was possible to represent the full meaning of 86% of ICD-10-PCS codes. Logical mapping between SNOMED CT and ICD-10-PCS is feasible but will be more productive if more SNOMED CT concepts can become fully-defined. Short of full logical matching, partial logical matches can also be useful in suggesting candidate maps for expert review and to support interactive post-coordination.

Leveraging Lexical Matching and Ontological Alignment to Map SNOMED CT Surgical Procedures to ICD-10-PCS.

In 2015 ICD-10-PCS replaced ICD-9-CM for coding medical procedures in the U.S. We explored two methods to automatically map SNOMED CT surgical procedures to ICD-10-PCS. First, we used MetaMap to lexically map ICD-10-PCS index terms to SNOMED CT. Second, we made use of the axial structure of ICD-10-PCS and aligned them to defining attributes in SNOMED CT. Lexical mapping produced 45% of correct maps and 44% of broader maps. Ontological mappings were 40% correct and 5% broader. Both correct and broader maps will be useful in assisting mappers to create the map. When the two mapping methods agreed, the accuracy increased to 93%. Reviewing the MetaMap generated body part mappings and using additional information in the SNOMED CT names and definitions can lead to better results for the ontological map.