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SNOMED CT can be implemented in a wide range of clinical record applications. These include systems developed for use with other code systems that have been adapted to support SNOMED CT as well as systems designed with the assumption that SNOMED CT would serve as the primary terminology. The SNOMED CT features that applications support and use may vary, partly due to differences in user requirements and partly due to development priorities. Against this background of variability, it is reasonable to ask what is a SNOMED CT implementation or what is a good SNOMED CT implementation. While there is not a single or simple answer to these questions, this section identifies some key dimensions which determine the capability of SNOMED CT enabled clinical record systems.

Each of the following sections describes a dimension and outlines a spectrum of capabilities ranging from absence of support (Level 0) to full support (Level 2). A mixture of Level 0 and Level 1 capabilities are likely to be found in existing systems that have been adapted to work with SNOMED CT. A system specifically developed to work with SNOMED CT should be expected to have capabilities that are at least at the high end of the Level 1 spectrum and should ideally have Level 2 capabilities.

The specification of different levels is not intended to suggest a step-by-step development path. Those needing to rapidly SNOMED CT enable an existing clinical record system are recommended to follow a two stage approach.

  1. Design, develop and deploy a revision to the current system to support Level 1 capabilities that meet known short or medium term requirements:
    • The level achieved in this stage will depend on customer requirements and the design limitation of the existing system.
  2. Design and develop a new or substantially revised system (including revised record structures) to support a mixture of high-end Level 1 and Level 2 capabilities:
    • The level at which this development is target should be one that meets anticipated medium to long term requirements;
    • Even if the initial target of the work is limited to the high-end of Level 1, the design should be sufficiently flexible to enable Level 2 capabilities to be added when required.

Developers who do not require a rapid deployment based on a revision of an existing systems are recommended to skip the first step and proceed to design and develop a flexible solution that utilizes the key strengths of SNOMED CT .

Each of the following sections describes one dimension that contributes to the overall implementation level. It is important to recognize that:

  • This is not a formal scoring scheme:
    • Some dimensions are more significant than others;
    • The significance of reaching a particular level depends on the nature of the application and the user requirements it seeks to address.
  • Many of the dimensions are inherently interdependent:
    • For example, Level 2 data entry capabilities are not compatible with Level 1 data storage.

Implementation Level - Scope of use

A clinical record system may use SNOMED CT expressions to represent some or all of the types of information outlined in the list below. The types of information for which SNOMED CT can be used may be limited by the structure used to store the electronic health record . The significance of these limitations depends upon the intended use of the clinical record system.

  • Level 0: No support for SNOMED CT expressions .
  • Level 1: Support for use of SNOMED CT limited to particular types of clinical data:
    • Addressing the requirements for a particular type of use;
    • Addressing a set of requirements specified by a particular organization .
  • Level 2: Support for consistent use of SNOMED CT across a broad scope of information types:
    • Providing a general purpose approach to the use of SNOMED CT within an electronic health record
    • Allowing configuration to vary the scope of coverage to meet specific requirements.

The following check-list identifies some of the electronic health record elements in which SNOMED CT expressions might be used. The list is not complete but it covers many of the areas in which use of SNOMED CT has been discussed in SNOMED International working groups. It is intended to assist consideration of the areas in which SNOMED CT should be used to meet the needs of users and organizations. The inclusion of an item in this list does not imply that the SNOMED CT International Release provides comprehensive content to populate that part of the record.

  1. Disorders, diagnoses and problems:
    • Problem list entries;
    • Admission diagnosis;
    • Discharge diagnosis;
    • Provisional or working diagnosis;
    • Differential diagnosis.
  2. Symptoms:
    • Presenting symptoms;
    • History of current condition;
    • Other symptoms.
  3. Allergies and adverse reactions:
    • Adverse reaction events;
    • Allergies and other propensities to adverse reactions.
  4. Procedures:
    • Operative procedures.
    • Diagnostic procedures.
    • Medications:
      • Current medication;
      • Prescriptions;
      • Dispensing records;
      • Drug charts.
    • Other therapeutic procedures:
      • Other therapy requests;
      • Other therapy delivery and outcomes.
  5. History:
    • Medical and surgical past history;
    • Medication history;
    • Family history.
  6. Examination findings:
    • Vital signs;
    • Clinical examination findings.
  7. Investigation information:
    • Laboratory investigations:
      • Laboratory investigation requests;
      • Laboratory investigation procedures;
      • Laboratory investigation results.
    • Diagnostic imaging:
      • Diagnostic imaging requests;
      • Diagnostic imaging procedures;
      • Diagnostic imaging results.
    • Other investigations:
      • Other investigation requests;
      • Other investigation procedures;
      • Other investigation result.
  8. Other types of clinical information:
    • Planned actions;
    • Risk, goal and expected outcomes;
    • Scale based assessments;
    • Progress notes.
  9. Administrative information:
    • Admission, transfer and discharge events.
  10. Other values:
    • Body sites, structures and locations;
    • Organisms;
    • Substances (other than drugs);
    • Pharmaceutical and biological products (drugs).

Implementation Level - Record structure

The logical model underlying the structure of the record has a direct effect on the ability of a SNOMED CT enabled clinical record system to take advantage of the features of SNOMED CT. An application may use an optimized proprietary internal representation of the electronic health record. However, consistent use of SNOMED CT across a range of applications requires a common reference model to which proprietary structures are mapped. In addition to this, the ways in which SNOMED CT expressions are used within a common reference information model need to be constrained to improve predictability and minimize ambiguity.

Implementation Level - Expression storage

Support for storing precoordinated and postcoordinated SNOMED CT expressions determines the extent to which SNOMED CT can be used to represent detailed information within an electronic health record .

Implementation Level - Data entry

The categorization in this section in based on the extent to which the system enables entry of SNOMED CT expressions . In addition, this section indicates the importance of a well-designed user-interface.


Another important data entry issue is the ease of use which depends on the usability, relevance and performance of searches. Where postcoordinated data entry is supported the approach to selecting or constructing postcoordinated expressions is also significant.

An attempt to categorize specific approaches to the user-interface is subjective as alternative user interfaces may be appropriate to different uses. However, for most environments a flexible range of configurable SNOMED CT aware user-interface tools is likely to offer a better user experience than reliance on a one-size fits all browser or search engine.

Implementation Level - Data retrieval

A major strength of SNOMED CT is its ability to support meaning based selective retrieval. The extent to which this feature is used by a clinical record system determines the value of entering and storing the data.

Implementation Level - Communication

The ability to send and received SNOMED CT expressions in messages or other communication is partially dependent on data entry, storage and retrieval capabilities. However, some types of communication may be supported by mapping or human-readable renderings even in the absence of internal support for SNOMED CT .