я пробовал это https://fhirtest.uhn.ca/baseDstu3/Observation?code=3141-9&code=20570-8&_count=1&patient=653528&_format=json&_pretty=true
но он вернулся
{"resourceType": "Bundle", "id": "dcd5cd91-de96-4a3e-a0c9-0cbfccf584e1", "meta": {"lastUpdated": "2018-01-13T06: 10: 21.398-05: 00"} , "type": "searchset", "total": 0, "link": [{"Relationship": "self", "url": "https://fhirtest.uhn.ca/baseDstu3/Observation?_Format=json&_pretty=true&code=3141-9&code=20570-8 "}]}