Mapping 3 procedure coding systems to the International Classification of Health Interventions (ICHI): coverage and challenges.

Objective: To study the coverage and challenges in mapping 3 national and international procedure coding systems to the International Classification of Health Interventions (ICHI).

Materials And Methods: We identified 300 commonly used codes each from SNOMED CT, ICD-10-PCS, and CCI (Canadian Classification of Health Interventions) and mapped them to ICHI. We evaluated the level of match at the ICHI stem code and Foundation Component levels. We used postcoordination (modification of existing codes by adding other codes) to improve matching. Failure analysis was done for cases where full representation was not achieved. We noted and categorized potential problems that we encountered in ICHI, which could affect the accuracy and consistency of mapping.

Results: Overall, among the 900 codes from the 3 sources, 286 (31.8%) had full match with ICHI stem codes, 222 (24.7%) had full match with Foundation entities, and 231 (25.7%) had full match with postcoordination. 143 codes (15.9%) could only be partially represented even with postcoordination. A small number of SNOMED CT and ICD-10-PCS codes (18 codes, 2% of total), could not be mapped because the source codes were underspecified. We noted 4 categories of problems in ICHI-redundancy, missing elements, modeling issues, and naming issues.

Conclusion: Using the full range of mapping options, at least three-quarters of the commonly used codes in each source system achieved a full match. For the purpose of international statistical reporting, full matching may not be an essential requirement. However, problems in ICHI that could result in suboptimal maps should be addressed.