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Using OpenCDS Concepts
Introduction
OpenCDS is a Clinical Decision Support system that is built around the notion of “clinical concepts.” There are many medical terminology systems and medical information exchange systems that refer to “concepts,” “concept descriptors (CDs),” or “concept unique identifiers (CUIs).”
When we refer to an OpenCDS Concept we are referring to specific implementation techniques within OpenCDS which have a strong dependence on most of these ideas, but in a concrete implementation.
The purpose of this document is to explain how we use all of these terms in OpenCDS, and how they relate to the general clinical understanding of “concepts.”
What is an “OpenCDS Concept?”
An OpenCDS Concept is an implementation technique in OpenCDS. As a big picture idea, OpenCDS has a structure and methods that are designed to allow the clinical user to develop decision support rules that are written using clinical concepts. We call those particular concepts “OpenCDS Concepts”, and they provide an interface to the detailed data that represents an instance of the clinical concept.
This means that the clinical rule writer can work using clinical terminology that clinicians understand. OpenCDS is designed to support rules written for the open-source Drools inferencing engine, using a domain specific language (DSL). The DSL makes it possible to write the rules so that they read just like the way a clinician would describe them, using terms (OpenCDS Concepts) that the clinician uses every day.
A medical informaticist, terminologist, or vocabulary expert then produces mappings of those concepts to values in a code system which is used in the actual clinical data. In many cases this will involve the use of terminology management systems with large databases, such as Apelon, First DataBank, and UMLS which support potentially large and internationally supported terminologies. However, it is possible to also create simple XML files that map proprietary or special-case codes to OpenCDS Concepts.
The clinical rules use OpenCDS Concepts in preference to references to the raw data, and the terminology mappings provide implementations of those concepts as lists of codes from one or more code systems. This separates the logic of the rules from the details of the data which the rules work on.
Therefore, an OpenCDS Concept is the interface between the clinical ideas and the data details that represent instantiations of the clinical concepts.
This section of this document will explain the following items, and discuss how they are used in OpenCDS:
- Concept Types
- OpenCDS Concepts
- Concept Instances
- Concept Mappings and Enumerations
The diagram below may make this relationship easier to visualize:
Following sections will discuss the techniques used to relate the patient data to the clinical concepts or ideas in the following software:
- JBoss Drools Guvnor (our supported authoring environment for KnowledgeModules, aka “rules” or generically as “knowledge”)
- OpenCDS Decision Support Service (our software service to do clinical decision support)
Concept Types
Definition:
Concept Types in OpenCDS is the term we use to refer to Java classes in OpenCDS that have been created for every “concept descriptor” (aka CD) and “template” found in the input data structured as a virtual medical record (vMR).
A Concept Type represents an entire category of information that can be found at several places in a clinical statement. Clinical statements are the basic building blocks of the vMR. The vMR is more fully discussed in a separate document named “Notes on OpenCDS internal Data Structure.” In addition, there are also a few additional Concept Types that deal with “templates” and some structural elements of the vMR.
In this document, I will always capitalize Concept Type when I am referring to those Java classes, and use lower-case when I am referring to the more common or generic notions of “concept.”
In some cases, we have also post-coordinated more than one CD in the input data (such as “body site” and “laterality”), because there may be a need to make decisions based on the combination of the two, or common coding systems for a procedure or problem may not provide adequate specificity without being associated with both values as a set. For example, we need to be able to say that a rash was present both on the right arm and the left leg.
Examples of Concept Types are a “ProcedureConcept,” an “AdverseEventAgentConcept,” a “ProblemConcept”, or a “MedicationClassConcept.”
Because they are based on specific data elements in the vMR, OpenCDS supports a fixed list of these Concept Types, including a few that are broad enough to fill most needs for an “other” category. While we can add more Concept Types if the need arises, we feel that the current list is useable. Supporting additional Concept Types is non-trivial, so it will not be done casually.
The authoritative list of supported Concept Types can always be found in the source code as separate files in the module opencds-vmr-1_0-internal as separate Java classes in the package org.opencds.vmr.v1_0.internal.concepts. These files have the name of the Concept Types as you would see them in a Drools Rule. They are also listed for a different purpose (building enumerations) in a Java class named “org.opencds.common.terminology.OpenCDSConceptTypes.java”.
The current list of Concept Types as of the time this document was written is shown on the next page:
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- Go to Apelon.opencds.org
- Login with the following parameters (password is “welcome2opencds”).
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- Apelon DTS with the built-in interface included in OpenCDS to produce XML files,
- any other terminology management system that can be configured to produce XML files, or
- by hand-crafted XML files.
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- Guvnor is a tool for doing two things:
- writing rules (which we sometimes refer to as “knowledge” about “clinical concepts”), and
- testing the logical validity of those rules
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- Patient has had 3 inpatient encounters for asthma in the past 1 year
- Patient has had 2 outpatient encounters for diabetes mellitus in the past 6 months
- Patient has had 1 emergency encounter for acute myocardial infarction in the past 10 days
- Patient has had 1 well-child encounter for EPSDT in the past 1 year
More information about using DSLs is found in the OpenCDS document named “OpenCDS Guvnor 5.3 DSL Best Practices.”
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- They are broad categories,
- They correspond to all the CD data elements in the vMR,
- They are relatively fixed (adding a new Concept Type requires a number of modifications to the OpenCDS software), and
- They are implemented as OpenCDS Concepts, maintained in Apelon DTS, and implemented by user-specified concept mapping specifications which are ultimately mapped to concept codes in terminology systems.
OpenCDS Internal Data, Concept Mapping Specifications, and Concept Mapping Instances
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