During the Jan 2024 connectathon, we ran into issues due to implementers using different systems for HCPCS.

• https://build.fhir.org/ig/HL7/davinci-crd/ValueSet-serviceRequestCodes.html says "Include all codes defined in urn:oid:2.16.840.1.113883.6.285"
• https://build.fhir.org/ig/HL7/davinci-pas/ValueSet-X12278RequestedServiceType.html says "Include all codes defined in http://www.cms.gov/Medicare/Coding/HCPCSReleaseCodeSets"
• PAS also calls out that CPT codes could appear in that same system
• I see PAS has an example using "http://www.cms.gov/Medicare/Coding/HCPCSReleaseCodeSets"
• I couldn't find an example in CRD
• The reference implementation appears to be using "https://bluebutton.cms.gov/resources/codesystem/hcpcs"

We should clarify what systems are valid for HCPCS level II, call out if CRD needs to handle multiple, and add an example to CRD.