The purpose of this document is to provide general information about creating maps from a Point of Service Terminology to a Reference Terminology.
This document is intended to provide new and experienced Business Analysts with introductory level information about terminology maps and is not intended to provide detailed information specific to mapping, why they are needed and how they might be created. Business Analysts who are preparing their Point of Service Terminology files in a healthcare information system will find this document of particular interest.
A map provides a link from one terminology to another. Mapping involves "matching" between a source term and a target concept that represents the same meaning, such as between two databases that contain the data elements that are meant to be similar but are called by different names. In most cases, the relationship is between the local point of service or vendor specific terms (the “source”) and the respective term from a Reference Terminology such as SNOMED CT® or LOINC® (the “target”). A mapping process simply matches the terms or words from a local system to the appropriate concept that represents the same meanings from a Reference Terminology.
Maps enable software and systems to meaningfully exchange patient information. Many Point of Service (POS) systems in a health care environment use a “local” terminology designed to support that particular POS system. These specific terminologies, although meaningful to the specific system they support, may lose their meaning when shared with other similar electronic systems (lab to lab, EMR to EMR, lab to EMR etc.). To overcome this disparity, Reference Terminologies are used to bridge the gap between these distinct “local” terminologies.
A map is intended to be used in electronic systems and is not exposed to the user at the point of service. The terminology used in the local system usually does not have to change. The target Reference Terminology is what is used to communicate with other systems. This facilitates interoperability between systems using their own local terminology. It also facilitates research and gathering information for statistical analyses.
Stakeholders that are sharing their data electronically with other electronic systems will need a map if they wish to retain their local or vendor specific descriptions but still share data electronically. Mapping their “local” terminology to a Reference Terminology allows the stakeholder to retain their existing and familiar coded concepts at the user interface and retain a link to previously collected data. Stakeholders who are not sharing their data electronically will need to have a specific business requirement other than sharing data electronically to justify mapping their local terminology.
There are two types of mapping relationships that can be used in a map. A map can use one or more types of relationships as needed.
There are two types of maps, bi-directional and unidirectional.
Unidirectional mapping goes from the source to the target. Bidirectional maps translate in both directions. Not all maps can be bidirectional; for instance, when multiple and differing terms in the source map to a single concept that represents the same meaning in the target. This map is represented in Figure 1.
Figure 1
In some maps, a database can act as a translation key from one source to the next, providing perhaps agreed upon user friendly descriptions that are mapped to the target. This map is represented in Figure 2.
Figure 2
In this map, local terms can be mapped to a specifically developed Terminology which acts as the buffer between the source terms and the target Reference Terminology. The specifically developed Terminology can be a common terminology that will be used by implementers (rather than using the source terminology or the Reference Target terminology) and is identified in the diagram as the “Translation Key Database”. This model involves more management and maintenance but provides implementations with the flexibility they may need to meet multiple requirements. It also provides an Interface Terminology, which provides common language for the users of the system that is not identical to the local terminology or the Reference Terminology, but something agreed on by the stakeholders.
There are two basic approaches to mapping. The preferred approach is a centralized approach but there are times when a decentralized approach is preferred.
a) Centralized Model – In this model, all the mapping is done for all organizations at a central source. All the files and the mapping are managed by the same group of people and are centrally located. Using the same people provides benefits:
There are some pitfalls of the centralized approach:
b) Decentralized Model – In this model, each organization performs their own mapping. Some benefits are:
Some of the pitfalls of this approach include:
There are several different kinds of resources required to do the mapping.
Technical resources may be required to support any mapping tool that is used. These resources will be responsible for loading software, providing software access and/or removing network restrictions. They may also:
Tools are required to map source terms to a concept that represents the same meaning in a Reference Terminology, and there are a variety available:
Anyone responsible for mapping should be specifically trained on the Reference Terminology that will be used. If there is sufficient access to the subject matter experts to support the business functionality, then a minimal knowledge of the source terms is required. If the access to the subject matter experts is limited, then a resource will require sound knowledge of the source terms and their use.
The Regenstrief website offers helpful information on using LOINC. (https://loinc.org/learn/)
SNOMED CT provides mapping material in its eLearning server. (https://elearning.ihtsdotools.org/)
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The Health Terminologies Community is a open forum for sharing and communicating on topics of terminologies and classifications and their use in Canada. We welcome all participants.