Value sets are a collection of codes drawn from one or more code systems, where the concepts included share a common scope of use. The codes and corresponding terms come from standard clinical vocabularies (such as Current Procedural Terminology [CPT], Systematized Nomenclature of Medicine Clinical Terms [SNOMED CT], RxNorm, and Logical Observation Identifiers Names and Codes [LOINC]). By providing a consistent, computable representation of clinical concepts, value sets support standardized data interpretation and interoperable exchange of health information.
Value set authors develop and maintain these collections by identifying the codes that appropriately represent the intended concept and scope of use. Measure developers and clinical decision support (CDS) developers then use value sets to identify relevant coded data, define patient or encounter populations, represent clinical conditions, observations, procedures, medications, and other concepts, and support applications such as quality measurement, clinical decision support, diagnostic workflows, and condition-specific order sets.
Value sets have a life cycle that includes development, review, publication, maintenance, and retirement. The Value Set Authority Center (VSAC), developed and maintained by the National Library of Medicine, provides tools to support the creation, maintenance, publication, and retrieval of value sets. The VSAC serves as the central repository for value sets used in CMS digital quality measures, including electronic clinical quality measures. Other value set repositories are available for specific programs and use cases, such as the Centers for Disease Control and Prevention’s Public Health Information Vocabulary Access and Distribution System.
The VSAC Support Center provides online information about VSAC access, value set lifecycles and workflow, measure developer and steward roles, and best practices for value set development. In addition, the VSAC Support Center offers archived users’ forums and release notes and provides links to VSAC publications.
Coded Data Elements
Coded data elements in quality measures are typically bound to (i.e., linked or mapped) to either
OR
- A value set: A defined collection of codes that are considered equivalent with respect to intended use in the context of that data element.
In quality measures, DRC and value sets identify the specific clinical or administrative concepts (for example patients, encounters, procedures, diagnoses, medications, or results) that should be considered with respect to the measure data element using the value set.
Value Set Creation Methods
Value set authors can create value sets in VSAC using three primary definition methods:
Extensional:
An extensional value set of concept codes and associated descriptions that are included for a specific purpose. Only the codes listed in the definition are included; related, parent, or descendant concepts are not implicitly included unless they are also explicitly listed.
In VSAC, an extensional value set contains concepts from a single code system.
Intensional:
An intensional value set is defined using logical rules or expressions that determine which concepts from a code system are included. These rules may use concept properties or relationships defined within the terminology, such as including all concepts that are descendants of a specified parent concept.
In VSAC, an intensional value set is defined using concepts from a single code system. Its expansion is calculated by applying the defined rules to a specified version of that code system.
Grouping:
A grouping value set is a collection of one or more existing value sets that share a common purpose. Grouping value sets are frequently used to combine member value sets based on different code systems so that the resulting value set expansion represents the intended concept across multiple terminologies.
For example, a grouping value set representing a clinical condition could include one member value set containing SNOMED CT concepts and another containing ICD-10-CM concepts.
In VSAC, grouping value sets contain member value sets rather than individual codes, and a grouping value set cannot contain another grouping value set. The expansion of the grouping value set combines the expanded codes from its member value sets.