Implementing Terminologies

This page examines the implementation aspects of terminologies, code systems and value sets. The vendor/implementer is handed an Implementation Guide (or a Normative Edition), something which specifies the interactions, static models and data types that have to be implemented. The Implementation Guide may specify the use of certain terminologies, code systems and value sets for some attributes, or it may leave it up to the implementer to make the appropriate choice.

FAQ

• No value set has been specified. What code system should I use?

No single medical terminology supports the full range of an applications’ requirements in the healthcare domain.

Agreement on a single terminology (esp. when it is to be used by multiple organizations) is a difficult process. The fact that mutual understanding (semantic interoperability) increasingly relies on terminologies mostly hits home after one has exchanged messages with different codes for a while.

• Implement first to raise awareness that harmonization of concept codes is a requirement

Application Design

The implementation of standardized medical terminologies in an application environment requires careful architectural design and tooling to support vocabulary access, authoring, distribution and maintenance tailored to the specific application use cases.

From the practical application perspective, it is inadequate to simply define a particular coding system and link it to a domain. When using postcoordinated concepts (whereby atomic entries in the vocabulary can be used to construct more complex concepts, e.g. SNOMED) the database structure has to be able to handle the more complex datatype (CD) and be able to regenerate the concept-encoding (the message snippet) exactly as it was received in order to maintain semantic consistency.

Terminologies are not stagnant and do not stand alone. Periodically published updates must be reconciled with applications that use them. In order to support longitudinal analysis it is important to maintain all concepts and their unique codes ever used to describe observations within a system. Concepts are required to be retired and mapped to new concepts as code systems are updated by the authors and should never be deleted. Such arduous vocabulary maintenance for application where updates may need to be applied to a multitude of code systems is best handled through centralized terminology services specifically designed for this purpose. There are several proprietary vendors who provide these services, and many larger clinical applications are developing their own terminology servicing systems.