Code Systems


Code Systems

When returning a code value in a Coding it is important to identify the namespace ("system") from which that code was drawn. The system is indicated by setting the relevant value into Coding.system.

So what is the relevant value? Well, it depends on where the code value came from.

Externally Defined

FHIR® curates a list of officially supported code systems, along with the system value which should be used.

For example, http://snomed.info/sct and http://loinc.org are externally defined code systems.

PKB has no control over the system values defined externally. The URLs used to identify the system are not required to be resolvable, and if they do resolve the content returned is undefined.

Externally Defined, PKB Hosted

PKB allows customers to upload their own code sets for some types of data.

By uploading their own code sets customers can facilitate more meaningful use of their data, such as having PKB map these code values to code values in another coding system, or to apply the customer's choice of privacy label to data points.

These code sets are not currently exposed from the FHIR API.

PKB Defined

There are several concepts for which PKB has defined a custom code set. For example, the PKB Privacy Labels will be represented as coded security labels in the FHIR metadata.

Each code set that PKB has defined has been given a URL for use in Coding.system throughout the FHIR API.

This URL is not guaranteed to resolve. It is PKB's intention that the URL resolves to helpful documentation whenever possible, but clients should not rely on this.

Please see the subpages for details of each code set defined by PKB.

Terminology Service

FHIR defines a set of functionality for interacting with code systems. For example, the ability to $lookup information about a known code.

A FHIR server which implements this functionality is known as a Terminology Service.

PKB does not currently offer this functionality.