Query: When was my last encounter for check up?, FHIR Resource: {'resourceType': 'Observation', 'status': 'final', 'category': [{'coding': [{'system': 'http://terminology.hl7.org/CodeSystem/observation-category', 'code': 'laboratory', 'display': 'Laboratory'}]}], 'code': {'coding': [{'system': 'http://loinc.org', 'code': '6158-0', 'display': 'Latex IgE Ab [Units/volume] in Serum'}], 'text': 'Latex IgE Ab [Units/volume] in Serum'}, 'subject': {'reference': 'urn:uuid:d25aa6d4-c827-34b6-89c7-4ca254ecb35c'}, 'effectiveDateTime': '2017-02-11T09:27:21+05:30', 'valueQuantity': {'value': 0.19481, 'unit': 'kU/L', 'system': 'http://unitsofmeasure.org', 'code': 'kU/L'}, 'interpretation': None}