Storing SNOMED CT encoded clinical records involves the storage of:
In some implementations of SNOMED CT this may also involve the storage of:
Clinical data which is stored using SNOMED CT will use SNOMED CT concept identifiers. SNOMED CT Identifiers are represented as a string consisting of between 6 and 18 digits. Further detail can be found in the Technical Implementation Guide: http://snomed.org/tig.
In most cases, the term selected by the user is also stored. The structural representation of stored clinical information is important. This must store similar information consistently, and the storage design must support effective querying.
User interfaces commonly restrict the data that can be selected by the user and stored. Electronic messages are also often constrained in terms of the permissible values that may be meaningfully included in each field. Decisions are made on whether some semantics, such as the priority for a procedure, is expressed in a reserved part of the message structure, or if it is expressed as part of the SNOMED CT expression within the message.
As part of implementation there may be a need to either:
The implementer should balance the cost of developing and maintaining an inter-terminology map, with their target quality for that map. Unless an existing terminology scheme represents clinical ideas in a comparable way to SNOMED CT then a perfect (i.e. lossless and reversible) map may not be possible.
Existing data entry interfaces may be modified to incorporate SNOMED CT in the required places, often as a direct replacement of another coding scheme.
Data entry features which may be enhanced or enabled using SNOMED CT include:
Attention is needed to identify which parts of the data entry interface are both in scope of SNOMED CT and which the implementer intends to be encoded using SNOMED CT. For example, when implementing a scored assessment with many questions, an implementer may choose to encode only the assessment result with SNOMED CT.
SNOMED CT allows a level of precision of meaning that is rarely matched by the content of proprietary terminology systems. For this and other reasons, there may need to be modifications or enhancements to the user interface and how it allows users to search, enter and express clinical ideas.
Routine scheduled maintenance of EHRs is anticipated and supported by SNOMED CT, which also has a program of continuous improvement. Unlike some classification or coding schemes, SNOMED CT updates, adds and inactivates content where it is useful to do so.
The changes to SNOMED CT content include changes to the status of a concept or term e.g. from active to inactive. Relationships between concepts change for a variety of reasons, including the refinement of a concept definition, in response to new medical understanding, or the introduction of new concepts.
The most common activities relating to changes to SNOMED CT content are:
Implementation of SNOMED CT within a system is not always concurrent to the adjustment of external electronic clinical data flows. The design of the electronic message, and the definition of the data extract which is used to populate the message, may need to be modified to accommodate its SNOMED CT payload. Similarly to data storage, an electronic message may require the inclusion of:
For a more extensive use of the features of SNOMED CT, messages may include:
Some implementation strategies include the bulk migration of data between different versions of their system or between different systems. In this or similar circumstances, the tasks of data Extraction, Transformation and subsequent Loading ['ETL'] are performed.
Data migration can include the use of:
SNOMED CT supports multiple different ways for a concept to be expressed and stored. A concept may also have some parts of its meaning expressed within the data structure itself. For example, some of the different ways in which SNOMED CT can be used to represent a 'family history of' a disorder include:
System outputs such as mandatory reports need to be supported at each implementation stage.
Reports can be used to guide resource allocation, for reimbursement, or for clinical quality evaluation, so the ability to provide these reports before and after any systems change is important to customers. Beyond the initial task of replicating existing reports and results, the analysis power of SNOMED CT can be exploited to generate new reports or types perhaps not previously possible.
SNOMED International distributes a map from SNOMED CT to ICD-10. This supports the generation of ICD-10 classified data from data originally recorded using SNOMED CT, or later mapped to SNOMED CT.
Transition to the use of SNOMED CT for clinical records will require, in some cases, re-development of the data processing to populate the reports. However, in many cases SNOMED CT will enhance previous reporting capabilities.