<?xml version="1.0" encoding="UTF-8"?><Observation xmlns="http://hl7.org/fhir">
  <id value="herd1"/>
  <!--   the mandatory status   -->
  <meta>
    <security>
      <system value="http://terminology.hl7.org/CodeSystem/v3-ActReason"/>
      <code value="HTEST"/>
      <display value="test health data"/>
    </security>
  </meta>
  <status value="final"/>
  <!--  category code is A code that classifies the general type of observation being made. This is used for searching, sorting and display purposes. -->
  <category>
    <coding>
      <system value="http://terminology.hl7.org/CodeSystem/observation-category"/>
      <code value="laboratory"/>
      <display value="Laboratory"/>
    </coding>
    <text value="Laboratory"/>
  </category>
  <!--  
    Observations are often coded in multiple code systems.
      - LOINC provides codes of varying granularity (though not usefully more specific in this particular case) and more generic LOINCs  can be mapped to more specific codes as shown here
      - snomed provides a clinically relevant code that is usually less granular than LOINC
      - the source system provides its own code, which may be less or more granular than LOINC
    -->
  <code>
    <!--   LOINC - always recommended to have a LOINC code   -->
    <coding>
      <system value="http://loinc.org"/>
      <code value="80219-9"/>
      <!-- more generic methodless LOINC -->
      <display value="Mycoplasma hyopneumoniae Ab sample/Positive control in Serum by Immunoassay"/>
    </coding>
    <!--   Also, a local code specific to the source system   -->
    <coding>
      <system value="http://acme.org/devices/clinical-codes"/>
      <code value="Mycoplasma"/>
      <display value="Mycoplasma"/>
    </coding>
    <text value="Mycoplasma hyopneumoniae - MHP"/>
  </code>
  <!--    subject is a herd of 2500 breding sows  -->
  <subject>
    <reference value="Group/herd1"/>
  </subject>
  <encounter>
    <display value="part of a health assurance program"/>
  </encounter>
  <effectiveDateTime value="2017-11-20"/>
  <!--   In FHIR, units may be represented twice. Once in the
    agreed human representation, and once in a coded form.
    Both is best, since it's not always possible to infer
    one from the other in code.

    When a computable unit is provided, UCUM (http://unitsofmeasure.org)
    is always preferred, but it doesn't provide notional units (such as
    "tablet"), etc. For these, something else is required (e.g. SNOMED CT)
     -->
  <valueQuantity>
    <value value="0.2"/>
    <unit value="% (sample/positive control)"/>
    <system value="http://unitsofmeasure.org"/>
    <code value="%"/>
  </valueQuantity>
  <interpretation>
    <coding>
      <system value="http://terminology.hl7.org/CodeSystem/v3-ObservationInterpretation"/>
      <code value="NEG"/>
      <display value="Negative"/>
    </coding>
    <text value="Negative"/>
  </interpretation>
  <!--  Specimen is a pooled serology sample of 30 animals. -->
  <specimen>
    <reference value="Specimen/pooled-serum"/>
    <display value="30 serum"/>
  </specimen>
  <referenceRange>
    <text value="&gt;0.4 Positive; 0.3 to 0.4 Suspect &lt; 0.3 Negative"/>
  </referenceRange>
</Observation>