Short answer: Base FHIR defines resources broadly so that every country and use case can use them. An implementation guide (IG) narrows them for a context: which elements are required or must-support, which code systems are bound to which elements, which extensions are allowed, with examples and tests. US Core defines the minimum for US health data exchange (aligned with USCDI); the International Patient Summary (IPS) defines a short cross-border summary; many countries publish their own base profiles.
What an IG contains
- Profiles (StructureDefinitions) that constrain resources, for example an Observation that must have a LOINC code and a UCUM unit.
- Value set bindings: which codes are allowed for an element.
- Extensions for data the base resource does not have.
- CapabilityStatements, examples, search requirements.
A resource "conforms" to an IG when it validates against its profiles; the HL7 validator checks this.
US Core vs IPS
US Core covers the data US systems exchange day to day (patients, problems, medications, labs, vital signs and more). The IPS covers what a doctor anywhere needs in an unplanned visit: allergies, medications, problems, immunizations and some more, packed in one document bundle, coded with international terminologies (SNOMED CT, LOINC). A system can support both. See our patient guide on the International Patient Summary.
In Anpheros
Anpheros generates an International Patient Summary for each person, validated with the HL7 validator against the IPS profiles. Developers: the International Patient Summary in FHIR and FHIR code systems.
Related pages
Sources
Frequently asked questions
What is a FHIR implementation guide?
A specification that narrows base FHIR for a country or use case with profiles, bindings and examples.
What does must-support mean?
That a system must be able to handle the element when the data exists; the exact meaning is defined by each IG.
What is the difference between US Core and the IPS?
US Core covers everyday US exchange; the IPS a short international summary for unplanned care.
How do I check that my resources conform?
Validate them against the IG's profiles, for example with the HL7 FHIR validator.
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