1 Introduction

The SNOMED CT International General/Family Practice Reasons for Encounter and/or Health Issues reference set (hereafter called the GP/FP Subset) and the map from the GP/FP Subset to the International Classification of Primary Care (ICPC-2) were both developed between 2010 and 2013 by the GP/FP Subset and ICPC mapping project group. This project ended on December 31, 2013 after field-testing of the products was completed. 

2 Background

In December 2009 a harmonization agreement was finalized between SNOMED International and the World organisation of Family Doctors (Wonca) to promote co-operation and collaboration between the two organisations. 

This agreement led to the formation of the International Family Physician/General Practitioner Special Interest Group (IFP/GP SIG) under the auspices of SNOMED International. The IFP/GP SIG was established to suggest content for the Systematized Nomenclature of Medicine – Clinical Terms (SNOMED CT®) related to general/family practice and to provide quality assurance for SNOMED CT content from the general/family practice perspective. SNOMED International's existing Primary Care Special Interest Group was converted to the IFP/GP SIG after the agreement was signed. 

The agreement contained a commitment to develop a mapping program, mapping relevant content in SNOMED CT to the International Classification of Primary Care, Version 2 (ICPC-2). Under the terms of the agreement, each task or project in the mapping program was to be managed by a mapping project group, comprised of members from the IFP/GP SIG, the WONCA International Classification Committee (WICC) and the SNOMED International's Mapping Special Interest Group. This project group was established in early 2010 and called the 'International GP/FP subset and ICPC mapping project group'. 

The subsets were first released as a candidate baseline in April 2014. Changes to the structure of the subsets were made following feedback from this release.   

3 Release content

3.1 Changes to the July 2018 release GP/FP subset

As a result of changes to the January 2019 release of SNOMED CT, the following concepts were removed from the set. Where a suitable concept was indicated, a replacement has been made. 

3.2 Overview of the GP/FP subset

Note: This document provides release information about the GP/FP subset. Release information about the map from the GP/FP subset to ICPC-2 can be found in the document SNOMED CT Refset to ICPC-2 Map Release Notes - January 2019. 

The GP/FP subset contains SNOMED CT concepts relating to two semantic data types commonly used in general/family practice electronic health records:

• Reasons For Encounter (RFEs)
• Health Issues

A reason for encounter was defined as:

"An agreed statement of the reason(s) why a person enters the health care system, representing the demand for care by that person. The terms written down and later classified by the provider clarify the reason for encounter and consequently the patient's demand for care without interpreting it in the form of a diagnosis. The reason for encounter should be recognized by the patient as an acceptable description of the demand for care" (WONCA Dictionary of General/Family Practice, 2003). 

A health issue was defined as:

"An Issue related to the health of a subject of care, as identified or stated by a specific health care party". This is further defined in the notes as "according to this definition, a health issue can correspond to a health problem, a disease, an illness" (Health Informatics – System of concepts to support continuity of care – Part 1: basic concepts (CEN/ISO FDIS 13940-1)). 

These definitions were used to define the scope of the GP/FP subset. The subset contains SNOMED CT concepts that represent terms commonly used to populate these semantic data types. 
The content of the subset covers the following:

• • Symptoms and signs
  • Disorders and diseases
  • Results
  • Family history
  • Allergies
  • Adverse drug reactions
  • Processes and procedures
  • Social history

Details on the development of the subset are available on request from info@snomed.org

4 General information about the GP/FP subset

Subsets act as the extensibility mechanism in SNOMED CT, allowing developers and users to customize SNOMED CT content to meet specific use cases. 

Content for the general/family practice subset was initially provided by the SNOMED International's General/Family Practice and ICPC-2 mapping project group. It is designed for use in general/family practice clinical settings within electronic health records (EHRs). It is intended for use as the 'core' subset for two commonly used data fields — reasons for encounter and health issues. 

4.1 Purpose of the GP/FP subset

To provide a subset of frequently used SNOMED CT concepts for use in general/family practice EHRs within the following data fields:

• Reason for encounter
• Health issue

4.2 Some example use cases of the GP/FP subset

4.2.1 Data entry – direct entry of SNOMED CT concepts from the GP/FP subset

During an encounter in his/her general/family practice, a GP/FP sees a patient who has presented with a newly identified health issue. The GP/FP enters the new health issue into the data field for 'health issue', and into a problem list (if appropriate) in his/her EHR using the GP/FP subset that has been incorporated in his/her EHR by the EHR software vendor. The GP/FP is presented with a validated list of potential terms from the subset, from which he/she selects the SNOMED CT concept that best represents the patient's health issue.

4.2.2 Electronic transfer of care (referrals, admissions, handovers, discharge)

A GP/FP wishes to transfer the care of a patient to a medical specialist for further investigation. The GP/FP's EHR contains the SNOMED CT GP/FP subset, and the GP/FP has entered all the patient's health issues into the EHR using the subset. An HL7 referral message is then constructed; containing SNOMED CT coded concepts from the patient's problem list. The message is sent electronically to the specialist who populates his/her EHR using the data contained in the message. This reduces the time needed to take a patient history and enter this data into the specialist's EHR.

4.2.3 Constraint of terminology use for population and sub-population analysis

A group of GPs are interested in comparing aspects of care across populations of GPs and their patients. The adoption of a subset will, to an extent, constrain the variability of coding of similar issues, conditions and situations that may confound data analysis where very large terminologies such as SNOMED CT are used without constraint.

4.3 Obtaining the GP/FP subset

Access within SNOMED International member countries is provided by the Member National Release Centre in each country, via the relevant Member page. Affiliates of SNOMED International in non-member countries can access the table through their Member Licensing and Distribution Service (MLDS) account. Please contact info@snomed.org for more information if required. 

4.4 Benefits of the subset

SNOMED CT is regarded as the leading global clinical terminology for use in EHRs. The GP/FP subset utilises the power of SNOMED CT by refining the subset to a list of concepts specific to those commonly used in General/Family practice. In this way assuring and enabling a SNOMED CT encoded system for recording aspects of the clinical record. This increases the usefulness of SNOMED CT for GPs/FPs because searches are targeted to the SNOMED CT concepts that GPs/FPs use most often, and, if implemented properly, users should be able to search and select a SNOMED CT concept quickly and easily. 

As stated in Section 4.5, the SNOMED CT GP/FP subset will be maintained and distributed after (and in line with) each release of the SNOMED CT International Release. 

4.5 Characteristics of the GP/FP subset

The GP/FP Subset contains the following characteristics:

• Only concepts with a status of 'current' (status = 0) have been included, ensuring that the only concepts included are active and able to be used for data entry.
• The Reason for encounter and Health issue subsets have been combined into one subset.

• A series of principles for the development of the GP/FP subset were created during the development phase of the project. These principles are documented in the SNOMED CT GP/FP subset and ICPC mapping project: Phase 2 project report.

• The GP/FP subset will be released using Release Format 2 (RF2) See Section 5.1 of the Technical Implementation Guide for further information about SNOMED CT release formats and RF2.

4.6 SNOMED CT target content

The GP/FP subset only contains SNOMED CT content from the following hierarchies:

• • Clinical finding
  • Event
  • Procedure
  • Situation with explicit context.

4.7 Known issues in the GP/FP subset

The GP/FP subset was developed using a 'bottom-up' approach, based on the terms frequently used in general/family practice to describe reasons for encounter and health issues. As a result, it does not contain all the SNOMED CT concepts that could be used to populate the reasons for encounter or health issue data fields in electronic health records. The IFP/GP Clinical Reference Group will add to the content of the subset over time, but it is not intended that the subset will contain all SNOMED CT concepts that could be used to populate these data fields. 

5 Implementation of the GP/FP Subset 

5.1 Implementation overview

• There are a variety of ways in which the GP/FP subset and map to ICPC-2 can be implemented, and it would be impossible to outline each possible scenario in this report.
• Vendors are encouraged to contact members of the IFP/GP Clinical reference Group to discuss specific implementation scenarios at info@snomed.org.
• Background about the creation and maintenance of subsets can be found in Section 7.9 of the SNOMED CT Technical Implementation Guide, and Section 7.6.3 discusses the application of Subsets
• The subset should be implemented in SNOMED CT enabled systems in order to access both additional content and also enable the power of SNOMED CT for retrieval and use of the information stored in systems. 

5.2 Implementation levels

The SNOMED CT Technical Implementation Guide describes three implementation levels for some aspects of SNOMED CT deployment. The three levels represent incremental capabilities for implementation broken down into specific dimensions including scope of use, record structure, expression storage, data entry, data retrieval and communication. Guidance provided in this section of the Technical Implementation Guide is also applicable to implementation of the GP/FP subset. 
It must be noted that the GP/FP subset does not inherently contain structures or content to support the implementation of post-coordinated expressions, as required for the highest implementation level within some dimensions. The decision to implement post-coordinated expressions must be made at the local level, with implementers choosing to allow users to created post-coordinated expressions in conjunction with use of the GP/FP subset. 

5.3 The user interface

Section 7.6 of the SNOMED CT Technical Implementation Guide provides recommendations and information for vendors about creating a user interface facilitating access to SNOMED CT concepts. 

5.4 Use of a secondary search mechanism

The GP/FP Subset contains concepts that are commonly used by GPs/FPs on an international basis, restricting the SNOMED CT concepts available to GPs/FPs to those concepts they are likely to use frequently. However, rare conditions are managed in general/family practice, and GPs/FPs may occasionally need to access a wider source of SNOMED CT concepts to populate their reasons for encounter or health issues.
For this reason, when implementing the GP/FP Subset implementers are strongly encouraged to implement a two-stage search mechanism, where users search for concepts in the GP/FP Subset in the first instance. Then, if a suitable concept cannot be found in the GP/FP Subset, a 'secondary search' is activated, allowing the search to be repeated using a broader set of relevant SNOMED CT concepts.

6 Effective Date and Maintenance

6.1 Effective date

The subset is aligned to the January 2019 SNOMED CT International Release.  The effectiveTime for the content has therefore been set to 20190131 (31st January 2019). 

Agreement of changes to both products will have clinical oversight by the International Family Practice/General Practice Derivatives Editorial Group. 
Requests for future changes will be accepted through the SNOMED International Request submission process or info@snomed.org. 

7 Technical Notes

RF2 package format

The RF2 package convention dictates that it contains all relevant files, regardless of whether or not there is content to be included in each particular release.  Therefore, the package contains a mixture of files which contain both header rows and content data, and also files that are intentionally left blank (including only a header record).  The reason that these files are not removed from the package is to draw a clear distinction between:

1. ...files that have been deprecated (and therefore removed from the package completely), due to the content no longer being relevant to RF2 in this or future releases, and 
2. ...files that just happen to contain no data in this particular release (and are therefore included in the package but left blank, with only a header record), but are still relevant to RF2, and could therefore potentially contain data in future releases.

This allows users to easily distinguish between files that have purposefully been removed or not, as otherwise if files in option 2 above were left out of the package it could be interpreted as an error, rather than an intentional lack of content in that release.