Stream: implementers
Topic: Search Parameters: base spec. vs IG Capability Statement
Kate Dech (Jan 08 2022 at 17:20):
Are implementers precluded from using a search parameter that is in the base FHIR specification for a resource if it is not explicitly listed in an IG's 'supported search' list?
My question is a general one but there is a specific IG that I can use as an example: CARIN BB EOB.
http://hl7.org/fhir/us/carin-bb/CapabilityStatement-c4bb.html#resource--details
EOB Supported Searches lists "_id, patient, _lastUpdated, type, identifier, service-date"
Base FHIR EOB has a search parameter called "coverage" that would be of benefit for us to use. http://hl7.org/fhir/R4/explanationofbenefit.html#search
Because the C4BB IG doesn't list coverage as a supported search parameter, does that mean we can not use it? Is the IG Capability Statement saying what you must support (but can support others from base specification?) or is it listing what you can only support?
Thanks!
cc: @Mona O @Bapi Behera
Elliot Silver (Jan 08 2022 at 18:08):
No, but...
The IG's CapabilityStatement is a minimum that implementers can expect, many systems will go beyond that minimum. To see what a system actually supports, you need to retrieve it's CapabilityStatement at runtime. If at that point you find it does more, go ahead and use the extra capabilities, but be prepared to fall back in case it doesn't (actually, you may want to be prepared in case it doesn't actually implement all that the IG CapabilityStatement says is expected).
Because the C4BB IG doesn't list coverage as a search parameter, you can't depend on it being available, but you're free to use it if it is.
(As a side note, the parameter names are actually dynamic, so the parameter with the "coverage" or "identifier" behavior may be called something else--although this is unlikely for core spec parameters. Theoretically, you need to check the runtime CapabilityStatement of the server you're connecting to to confirm what name the search parameter canonical maps to on your server.)
Corey Spears (Jan 08 2022 at 18:35):
What Elliot says is correct.
To add additional context specific to the CARIN BB IG: Coverage was not included as a search parameter because BlueButton interactions are patient/member and payer specific. Generally speaking, a member usually has only one coverage per payer. There are exceptions to this depending on how the payer decides to implement the IG in relation to how they are managing coverage. Payers are free to go above and beyond the minimal requirements of the IG, but don't expect payers to support it.
Note also that the FHIR standard says that servers SHOULD ignore unknown or unsupported parameters, but this is not a requirement (https://hl7.org/fhir/r4/search.html#errors). A server may reject queries with unknown parameters.
Yunwei Wang (Jan 09 2022 at 16:59):
Server SHALL support those search parameters to be conformant with this IG. See the Search Parameter Summary in this section. Server MAY support other search parameters.
Last updated: Apr 12 2022 at 19:14 UTC
