
**Example Usage Scenarios:**

The following are example usage scenarios for this profile:

-  Query for clinical tests or diagnostic imaging results for a patient.
-  [Record or update] clinical tests or diagnostic imaging results belonging to a Patient

### Mandatory and Must Support Data Elements

The following data elements must always be present ([Mandatory] definition) or must be supported if the data is present in the sending system ([Must Support] definition). They are presented below in a simple human-readable explanation. Profile-specific guidance and examples are provided as well. The [Formal Views] below provides the formal summary, definitions, and terminology requirements.

**Each Observation Must Have:**

1.   a status
2.   a category code
3.   a [LOINC] code, if available, which tells you what is being measured
4.   a patient

**Each Observation Must Support:**

1. encounter associated with Observation
2. a time indicating when the measurement was taken
3. a performer<sup>2</sup>
4. a result value
   - if the result value is a numeric quantity, a standard [UCUM] unit
5. a reason why the data is absent<sup>1</sup>

<sup>1,2</sup> see guidance below

### Profile Specific Implementation Guidance

This section provides detailed implementation guidance for the US Core Profile to support implementation and certification.

- See the [US Core Laboratory Result Observation Profile] to represent laboratory test results.
{% include observation_guidance_1.md category="procedure, exam or laboratory" recommendation="Servers **SHOULD** use the base FHIR [Observation Category Codes].<sup>[§][CONF-0423]</sup>" %}
- For a *starter set* of example clinical test LOINC codes, see [Appendix B in U.S. Core Data for Interoperability (USCDI) Task Force 2021 HITAC Phase 3 Recommendations Report Letter].
{% include provenance-author-bullet-generator.md footnote-symbol='<sup>2</sup>' %}

{% include link-list.md %}
