Towards Data Interoperability: Practical Issues in Terminology Implementation and Mapping (2005)

Introduction: Many health care organizations face the challenge of data interoperability. Standard vocabularies are a means of encoding data for exchange, comparison or aggregation among systems. However, there are issues concerning their use in the Electronic Health Record (EHR). Approach: The 3M Healthcare Data Dictionary (HDD) integrates and supplements standard vocabularies, presenting a master reference terminology used to encode data in the Clinical Data Repository (CDR). The HDD content is cross-referenced to standard vocabularies. Each HDD concept is identified by a Numerical Concept IDentifier (NCID), and the identifiers from external terminologies are mapped to it. NCIDs are used to encode the data in the CDR. The code in the incoming message to the CDR is translated by the HDD to the corresponding NCID for storage. If the sending system uses non-standard codes, then these legacy codes are first mapped into the HDD. Through mapping, the HDD translates between standard vocabularies, between legacy systems, and between a legacy system and a standard vocabulary. For external data exchange, the HDD translates the encoded data from NCIDs to a standard code. Discussion: An alternative approach is to use the identifiers of standard vocabularies, instead of NCIDs, to encode data in the CDR. While standardization and interoperability are achieved, challenges remain. Shift in meaning of a standard code: If a standard code is used to encode data, then, if the meaning of the code changes over time (code reuse), the data will be interpreted incorrectly. HDD concepts never change their meanings, thus the reused code will be mapped to a different concept, and data encoded with NCIDs will not be misinterpreted. Removal of standard codes: If data is encoded with a standard code that has since been removed by the vocabulary, the data is no longer interpretable. An NCID is never deleted; an inactive standard code is marked as such without affecting the CDR data. Lack of comprehensive standard codes: A standard vocabulary may not provide all the codes that correspond to the entire set of data in current use. The HDD provides all concepts needed to encode data in the CDR. If a code is later assigned by the standard vocabulary, it is mapped to its corresponding NCID in the HDD, with no updates required for the CDR. Local extensions: Local extensions are codes added at each facility. The HDD coordinates all local extensions within an organization so the data is standardized enterprise-wide. Historical patient data: If historical data has been encoded with non-standard vocabularies, then, encoding the data using standard vocabularies from this point onwards would result in the historical data being not interoperable. The HDD maps legacy codes to NCIDs to ensure interoperability for historical data. Conclusion: The lack of data interoperability is a key obstacle to realizing the full benefits of an EHR. Standard vocabularies provide the means for interoperability, but present problems surrounding their use. The HDD approach evolved from meeting user needs. We share our experience in the interest of promoting data standardization.