Postcoordination with SNOMED CT offers significant benefits for users who need to capture and express clinical meanings accurately. Postcoordination enhances the flexibility and expressivity of SNOMED CT, making it more adaptable to current clinical practice. However, postcoordination also presents a variety of challenges, encompassing both human and technical issues that are crucial to handle as part of an implementation, ensuring that postcoordination is used judiciously and consistently to maximize its benefits while minimizing its potential drawbacks.

Benefits

Two overall benefits can be described for postcoordination:

Postcoordination supports the ability to express or capture new meanings or clinical ideas that are not already in SNOMED CT

SNOMED CT implementers without the means to create and manage a proper extension may require clinical meanings to be represented using SNOMED CT without being dependent on specific precoordinated concepts existing. In such cases, postcoordination may be considered as part of a SNOMED CT implementation.

Postcoordination supports the ability to compose clinical meanings from separate input values and then classify to identify existing precoordinated content

Some SNOMED CT implementations are dependent on a fixed information structure, user requirements may enforce a specific way of entering clinical data, or new clinical meanings are created dynamically (for example within a natural language processing tool). These are cases in which implementations may require clinical meanings to be represented as expressions.

Challenges

To realize the benefits of postcoordination, careful analysis of the following described challenges needs to be undertaken and solutions need to be implemented.

Tooling and guidance in the area of postcoordination are still in a developmental stage

A key challenge for the implementation of postcoordination is the lack of mature or well-developed tools and practical experience within this area.

Creating expressions, in a way that conforms to all the rules and consistent with existing content in order to classify correctly, is not simple!

As described in 2.2 Expression Syntax and 2.3 Concept Model and Editorial Guidance, expressions that represent the desired semantics must follow both terminological and editorial principles of SNOMED CT. In addition, expressions should be consistent with the modeling applied for the released SNOMED CT content. Therefore, the creation of expressions should be performed by people with the required knowledge, or assisted by tools that facilitate the proper creation of expressions. 

Expressions are tied to a specific SNOMED CT release and upgrading that release requires maintenance

Maintenance processes need to be established to ensure that the expressions used in the system continue to work properly with the updated version of SNOMED CT. 

Interpretation by humans is a challenge

Generated expressions may not use natural language

Task of manually assigning terms that accurately represent the meaning of expressions require training and is cognitively demanding

Interpretation by machines is a challenge

Advanced tooling is required to create, maintain, understand and use expressions