STU3 Candidate

This page is part of the FHIR Specification (v1.8.0: STU 3 Draft). The current version which supercedes this version is 5.0.0 . For a full list of available versions, see the Directory of published versions . Page versions: R5 R4B R4 R3

10.1.18 Resource Observation - Operations

This resource has 1 operation associated with it:

$stats Observation Statistics

For more information about operations, including how they are invoked, see Operations .

10.1.18.1 Observation Statistics

The Statistics operation performs a set of statistical calculations on a set of clinical measurements such as a blood pressure as stored on the server. This operation is focused on Observation resources with valueQuantity elements that have UCUM unit codes.

The set of Observations is defined by 4 parameters:

  • the subject of the observations for which the statistics are being generated ( subject )
  • which observations to generate statistics for ( code and 'system', or 'coding')
  • the time period over which to generate statistics ('duration' or 'period')
  • the set of statistical analyses to return ( statistic ).

Possible statistical analyses (see StatisticsCode ):

  • average ("Average"): The mean of N measurements over the stated period
  • maximum ("Maximum"): The maximum value of N measurements over the stated period
  • minimum ("Minimum"): The minimum value of N measurements over the stated period
  • count ("Count"): The [number] of valid measurements over the stated period that contributed to the other statistical outputs
  • totalcount ("Total Count"): The total [number] of valid measurements over the stated period, including observations that were ignored because they did not contain valid result values
  • median ("Median"): The median of N measurements over the stated period
  • std-dev ("standard deviation"): The standard deviation of N measurements over the stated period
  • sum ("sum"): The sum of N measurements over the stated period
  • variance ("variance"): The variance of N measurements over the stated period
  • %20 ("20th percentile"): The 20th Percentile of N measurements over the stated period
  • %80 ("80th percentile"): The 80th Percentile of N measurements over the stated period
  • 4-lower ("lower quartile"): The lower Quartile Boundary of N measurements over the stated period
  • 4-upper ("upper quartile"): The upper Quartile Boundary of N measurements over the stated period
  • 4-dev ("quartile deviation"): The difference between the upper and lower Quartiles is called the Interquartile range. (IQR = Q3-Q1) Quartile deviation or Semi-interquartile range is one-half the difference between the first and the third quartiles.
  • 5-1 ("1st quintile"): The lowest of four values that divide the N measurementsinto a frequency distribution of five classes with each containing one fifth of the total population
  • 5-2 ("2nd quintile"): The second of four values that divide the N measurementsinto a frequency distribution of five classes with each containing one fifth of the total population
  • 5-3 ("3rd quintile"): The third of four values that divide the N measurementsinto a frequency distribution of five classes with each containing one fifth of the total population
  • 5-4 ("4th quintile"): The fourth of four values that divide the N measurementsinto a frequency distribution of five classes with each containing one fifth of the total population

If successful, the operation returns an Observation resource for each code with the results of the statistical calculations as component value pairs where the component code = the statistical code. The Observation also contains the the input parameters patient , code and duration parameters. If unsuccessful, an OperationOutcome with an error message will be returned.

The client can request that all the observations on which the statistics are based be returned as well, using the include parameter. If an include parameter is specified, a limit may also be specified; the sources observations are subsetted at the server's discretion if count > limit. This functionality is included with the intent of supporting graphical presentation

Formal Definition (as a OperationDefinition ).

URL: [base]/Observation/$stats

In Parameters:
Name Cardinality Type Binding Profile Documentation
subject 1..1 uri

The subject of the relevant Observations, which has the value of the Observation.subject.reference. E.g. 'Patient/123'. Reference can be to an absolute URL, but servers only perform stats on their own observations

code 0..* string

The test code(s) upon which the statistics are being performed. Provide along with a system, or as a coding. For example, the code = "45667-2" will evaluate all relevant Observations with this code in Observation.code. For LOINC codes that are panels, (e.g. 55284-4) this means to include all the individual codes that are part of a panel

system 0..1 uri

The system for the code(s). Or provide a coding instead

coding 0..* Coding

The test code upon which the statistics are being performed, as a Coding

duration 0..1 decimal

The time period of interest given as hours. For example, the duration = "1" represents the last hour - the time period from on hour ago to now

period 0..1 Period

The time period over which the calculations to be performed, if a duration is not provided

params 1..* code

average|max|min|count The statistical operations to be performed on the relevant operations. Multiple statistics operations can be specified. These codes are defined here

Out Parameters:
Name Cardinality Type Binding Profile Documentation
return 1..* Observation

A set of observations, one observation for each code, each containing one component for each statistic. The Observation.component.code contains the statistic, and is relative to the Observation.code and cannot be interpreted independently. The Observation will also contain a subject, effectivePeriod, and code reflecting the input parameters. The status is fixed to final .

source 0..* Observation

Source observations on which the statistics are based

10.1.18.1.1 Examples

Get the average, min, max and count of a series of BP measurements for a patient (Request): 

GET [base]/Observation/$stats?subject=Patient/123&code=55284-4&duration=1&statistic=average&statistic=min&statistic=max&statistic=count

Response: 

<?xml version="1.0" encoding="UTF-8"?>
<!--
  The outcome for this particular operation is 2 Observation resources - one for the diastolic 
  and one for the systolic components, because the requested LOINC code is a panel code 
-->
<Parameters xmlns="http://hl7.org/fhir">
  <parameter>
    <name value="return"/>
    <resource>
      <Observation>
        <status value="final"/>
        <code>
          <coding>
            <system value="http://loinc.org"/>
            <code value="8462-4"/>
            <display value="Diastolic blood pressure"/>
          </coding>
        </code>
        <subject>
           <reference value="Patient/123"/>
        </subject>
        <effectivePeriod>
           <start value="2016-05-25T19:26:16Z"/>
           <end value="2016-05-25T20:26:16Z"/>
        </effectivePeriod>
        <!--The Observation.component.code is relative to the Observation.code and cannot be interpreted independently.-->
        <component>
           <code>
              <!--   the average parameter code -->
              <coding>
                 <system value="http://hl7.org/fhir/observation-paramcode"/>
                 <code value="average"/>
                 <display value="Average"/>
              </coding>
           </code>
           <valueQuantity>
              <value value="79.7"/>
              <unit value="mmHg"/>
              <system value="http://unitsofmeasure.org"/>
              <code value="mm[Hg]"/>
           </valueQuantity>
        </component>
        <component>
           <!--  the max parameter code -->
           <code>
              <coding>
                 <system value="http://hl7.org/fhir/observation-paramcode"/>
                 <code value="max"/>
                 <display value="Maximum"/>
              </coding>
           </code>
           <valueQuantity>
              <value value="110"/>
              <unit value="mmHg"/>
              <system value="http://unitsofmeasure.org"/>
              <code value="mm[Hg]"/>
           </valueQuantity>
        </component>
        <component>
           <!--  the min parameter code -->
           <code>
              <coding>
                 <system value="http://hl7.org/fhir/observation-paramcode"/>
                 <code value="min"/>
                 <display value="Minimum"/>
              </coding>
           </code>
           <valueQuantity>
              <value value="56"/>
              <unit value="mmHg"/>
              <system value="http://unitsofmeasure.org"/>
              <code value="mm[Hg]"/>
           </valueQuantity>
        </component>
        <component>
           <!--  the count parameter code -->
           <code>
              <coding>
                 <system value="http://hl7.org/fhir/observation-paramcode"/>
                 <code value="min"/>
                 <display value="Minimum"/>
              </coding>
           </code>
           <valueQuantity>
              <value value="7"/>
              <system value="http://unitsofmeasure.org"/>
              <code value="{observations}"/>
           </valueQuantity>
        </component>
     </Observation>
    </resource>
  </parameter>
  <parameter>
    <name value="return"/>
    <resource>
      <Observation>
        <status value="final"/>
        <code>
           <coding>
              <system value="http://loinc.org"/>
              <code value="8462-4"/>
              <display value="Diastolic blood pressure"/>
           </coding>
        </code>
        <subject>
           <reference value="Patient/123"/>
        </subject>
        <effectivePeriod>
           <start value="2016-05-25T19:26:16Z"/>
           <end value="2016-05-25T20:26:16Z"/>
        </effectivePeriod>
        <!--The Observation.component.code is relative to the Observation.code and cannot be interpreted independently.-->
        <component>
           <code>
              <!--   the average parameter code -->
              <coding>
                 <system value="http://hl7.org/fhir/observation-paramcode"/>
                 <code value="average"/>
                 <display value="Average"/>
              </coding>
           </code>
           <valueQuantity>
              <value value="79.7"/>
              <unit value="mmHg"/>
              <system value="http://unitsofmeasure.org"/>
              <code value="mm[Hg]"/>
           </valueQuantity>
        </component>
        <component>
           <!--  the max parameter code -->
           <code>
              <coding>
                 <system value="http://hl7.org/fhir/observation-paramcode"/>
                 <code value="max"/>
                 <display value="Maximum"/>
              </coding>
           </code>
           <valueQuantity>
              <value value="110"/>
              <unit value="mmHg"/>
              <system value="http://unitsofmeasure.org"/>
              <code value="mm[Hg]"/>
           </valueQuantity>
        </component>
        <component>
           <!--  the min parameter code -->
           <code>
              <coding>
                 <system value="http://hl7.org/fhir/observation-paramcode"/>
                 <code value="min"/>
                 <display value="Minimum"/>
              </coding>
           </code>
           <valueQuantity>
              <value value="56"/>
              <unit value="mmHg"/>
              <system value="http://unitsofmeasure.org"/>
              <code value="mm[Hg]"/>
           </valueQuantity>
        </component>
        <component>
           <!--  the count parameter code -->
           <code>
              <coding>
                 <system value="http://hl7.org/fhir/observation-paramcode"/>
                 <code value="count"/>
                 <display value="Count"/>
              </coding>
           </code>
           <valueQuantity>
              <value value="7"/>
              <system value="http://unitsofmeasure.org"/>
              <code value="{observations}"/>
           </valueQuantity>
        </component>
      </Observation>
    </resource>
  </parameter>  
</Parameters>