Query an IHE PDQm server for patient demographics using FHIR Patient search parameters

Verified steps

1. Identify the PDQm Patient Demographics Supplier actor endpoint; the supplier exposes a FHIR R4 Patient search endpoint conforming to the IHE PDQm v3.1.0 IG
2. Submit a PDQm query (IHE transaction ITI-78): GET [base]/Patient?family=<last-name>&given=<first-name>&birthdate=<date> using standard FHIR Patient search parameters; PDQm mandates support for family, given, identifier, telecom, gender, birthdate, address, and mothersMaidenName
3. For cross-domain queries, include the targetSystem parameter (PDQm-specific) to restrict results to identifiers from a specific patient identity domain: GET [base]/Patient?identifier=<value>&targetSystem=<system-oid>
4. Parse the returned FHIR Bundle (type=searchset) and inspect each Patient entry; evaluate match quality using Bundle.entry.search.score if the server provides it, or using your own criteria on returned demographics
5. Handle the 'too many results' response: the supplier MAY return an OperationOutcome with a warning and a partial result set — implement UI flows for disambiguation when multiple candidate patients are returned
6. If needed, narrow the query iteratively by adding more demographics (e.g., adding address or telecom) until a single match or a manageable candidate set is returned