Classifying Codings

Many use cases require additional information about a term within a domain. For example, it may be useful to summarize conditions in a higher level clinical category, extract the strength of a medication, or group lab observations for trending. The Terminology API uses reference value sets to serve several different functions:

  • Categorization (e.g., grouping problems into chronic vs. acute)
  • Attributes (e.g., identifying medication ingredients)
  • Filtering/Querying (e.g., finding discharge summaries within reports)

The Classify operations provide abstractions for the most commonly used value sets for each domain, which make the Terminology API easy to understand and use. The Terminology API also provides direct access to value sets through the FHIR ValueSet resource for advanced use cases.


The following classify operations are available:

Operation Input Reference Code Systems

Provides clinical categories, acute vs. chronic, risk adjustment categories, and COVID status.

  • ICD-10-CM
  • ICD-9-CM-Diagnosis

Provides RxNorm properties, MEDRT therapeutic class, and COVID-related category (including vaccination).

  • RxNorm
  • NDC
  • CVX

Provides LOINC properties and COVID test type.


Alternatively, you can use the $classify operation which is a superset of the individual domain-specific classify operations.