FHIR search explained: parameters, prefixes, modifiers, _include and paging

Short answer: FHIR search is a REST query: GET [base]/[ResourceType]?parameter=value. Each resource has defined search parameters with a type, and values can be refined with prefixes (ge, lt…) and modifiers (:exact, :missing…). Results come back as a searchset Bundle with paging links.

Parameter types and examples

• token (codes): Observation?code=http://loinc.org|4548-4
• date: Observation?date=ge2025-01-01&date=lt2026-01-01; prefixes eq, ne, gt, lt, ge, le, sa, eb, ap.
• reference: Observation?subject=Patient/123 (or patient=123).
• string: Patient?family=smith (starts-with by default; :exact and :contains modifiers).
• quantity: Observation?value-quantity=gt7|http://unitsofmeasure.org|%.

Combine with & (and); repeat values separated by commas for or: code=http://loinc.org|2093-3,http://loinc.org|2571-8.

Including, sorting and paging

• _include=Observation:subject adds the referenced Patient to the results; _revinclude=Provenance:target adds resources that point to them.
• Chaining: Observation?subject:Patient.family=smith.
• _sort=-date sorts newest first; _count=50 sets the page size; follow link[relation=next] for the next page rather than building offsets yourself.
• _summary=count returns only the total.

In Anpheros

Anpheros Platform supports standard FHIR search on the patient's resources, within the scopes the patient granted. Developers: getting started, the FHIR sandbox and limits.

Related pages

• FHIR Bundle explained
• FHIR Observation explained

Sources

• HL7 FHIR R4: Search

Frequently asked questions

How do I search FHIR Observations by LOINC code?

Observation?code=http://loinc.org|4548-4 (system|code).

How do I search by date range?

Repeat date with prefixes: date=ge2025-01-01&date=lt2026-01-01.

What does _include do?

Adds the resources referenced by the results, such as the Patient of each Observation, to the same Bundle.

How do I page through results?

Follow the next link in the returned Bundle; set page size with _count.

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Anpheros builds a medical record that the patient controls and can share with any clinic, on an HL7 FHIR R4 platform, based in the EU. These guides help you understand and organise your health; they do not replace your doctor.

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