Query Observation resources using LOINC codes to retrieve lab results and vital signs

Steps

1. Search observations for a patient filtered by LOINC code: GET [base]/Observation?patient=[id]&code=http://loinc.org|[LOINC-code]; use the canonical LOINC system URI http://loinc.org.
2. To query multiple LOINC codes at once, use a comma-separated list: code=http://loinc.org|2160-0,http://loinc.org|33914-3 (this is an OR within the code parameter).
3. Filter by date range with date=ge[YYYY-MM-DD]&date=le[YYYY-MM-DD] to limit results to a clinical window.
4. Access valueQuantity.value and valueQuantity.unit for numeric results; check valueCodeableConcept for coded results; check component[] for panel observations like blood pressure.
5. Inspect Observation.status; typical values are 'final', 'preliminary', 'amended', 'cancelled'; exclude non-final statuses for clinical decision use.
6. For vital sign panels (e.g., blood pressure), retrieve the component array: component[0].code (systolic LOINC) and component[0].valueQuantity, and similarly for component[1] (diastolic).