Find Lab Results

Labs may be found from the DiagnosticReport resource. DiagnosticReports with category=LAB may contain one or more results (lab values) as Observation resources. Lab results should be queried by DiagnosticReport rather than from the Observation resource directly in order to:

• Gain context required to interpret the observation (e.g., observation = ‘glucose’ requires the report to know whether it is a blood glucose or a urine glucose, etc.)
• Group multiple Observations for a panel of labs (such as a metabolic panel which contains sodium, glucose, BUN, etc.).
• Include a reference to identify the ordering clinician.
• Include a document (as a Binary resource) if a lab result is not returned as a discrete field. For detail on how to use Binary resources, see Find a Discharge Summary.

Retrieve Lab Results or Reports via DiagnosticReport

Lab results can be queried via DiagnosticReport. Multiple results, such as from a lab panel, may be grouped within each DiagnosticReport resource.

• Use DiagnosticReport.category=LAB to limit results to laboratory.
• Be sure to use _include=DiagnosticReport:result which will return a list of Observation and/or Binary resources.

Retrieve vital signs via Observation

Vital signs (e.g., Blood Pressure, Height, Weight, Temperature, Resipiratory Rate, Oxygen Saturation) can be queried via Observation. Each result will be returned as a separate Observation.

• To retrieve vital signs via Observation resource, use Observation.category=vital-signs.

Filter by ValueSet

• DiagnosticReport and Observation resources can be filtered by Value Set by code:in=[ValueSet URI].
• To use a LOINC value set,
  • First, identify the LOINC Parts which will define your filter. This can be done most easily by identifying a few target codes and noting the attributes which most closely meet your needs on the LOINC search site: https://search.loinc.org/searchLOINC/search.zul.
  • Then, query for https://[YOUR_FHIR_ENDPOINT]/ValueSet?version=[LOINC Part Type]&name=[LOINC Part Value] to retrieve the [ValueSet URI]. The following are are the strings to use for the [LOINC Part Type], aligned with those you’ll see as column headers in the LOINC Search results:
    • LOINC-Class (e.g., Cardiology, Radiology)
    • LOINC-ClassType (1=Laboratory class; 2=Clinical class; 3=Claims attachments; 4=Surveys)
    • LOINC-Component (The analyte or attribute being measured or observed. E.g., sodium, body weight.)
    • LOINC-MethodType (e.g., Immunoassay, Visual Count)
    • LOINC-Property (e.g., Mass, Count, Concentration)
    • LOINC-ScaleType (e.g., Quantitative, Narrative, Document)
    • LOINC-System (e.g., Blood, Liver)
    • LOINC-TimeAspect (e.g., Point in time, 24 Hours)
  • Finally, use the fully-specified [ValueSet URI] in the DiagnosticReport or Observation query.
• Only one value set is required for a query, though multiple can be used.
  • For Union (OR) of value sets, place each [ValueSet URI] within a comma-delimited list, e.g., code:in=[ValueSet URI 1],[ValueSet URI 2],[ValueSet URI 3]
  • For Intersection (AND) of value sets, place each [ValueSet URI] within a separate parameter, e.g., code:in=[ValueSet URI 1]&code:in=[ValueSet URI 2]&code:in=[ValueSet URI 3].
  • A combinatino of Union and Intersection can be used.

Example Lab Test Queries

Grouping Labs

DiagnosticReport resources can be used to group Lab results into panels. In addition, many clinical use cases group results by Observation.code (where system=http://loinc.org) or Observation.code.text to enable trending over time.

Real-World Data Considerations

• Lab description/display
  • Use both the DiagnosticReport and Observation to provide sufficient context for users
    • Some source systems send the lab description in the DiagnosticReport and little information in the Observation (e.g., report lists ‘Blood Glucose’ and observation lists ‘CHEMISTRY’)
    • Other source systems send important context in the DiagnosticReport (e.g., report lists ‘presence in urine’ and observation lists ‘glucose’)
    • Often panels are grouped by DiagnosticReport (e.g., report lists ‘complete metabolic panel - blood’ and observations include ‘glucose’, ‘sodium’, etc)
    • Depending on the use case and UI design, you may simplify how the data is presented to users where DiagnosticReport.code and/or .display lists things such as ‘Misc’, ‘Other’, or ‘Observation’ or if there is a single child Observation which has the same .code and/or .display as those in the report
  • When sufficient codes and context are recieved in source data, HIEBus maps labs to LOINC; To make use of LOINC reference mapping, we recommend doing the following to populate user display:
    • First, use DiagnosticReport.code.coding.display and Observation.code.coding.display where userselected=false AND system=http://loinc.org
    • If LOINC mapping is unavailable, use the source descriptions DiagnosticReport.code.coding.display and Observation.code.coding.display where userselected=true
• Lab Provider - Lab Provider (e.g., Quest, LabCorp) can be found in Observation.performer which gives a Reference(Practitioner).
• Ordering Clinician - If available, the provider that ordered a lab can be found by
  • Observation.extension('http://careevolution.com/fhirextensions#observation-reportReference')
  • which gives a Reference(DiagnosticReport.basedon)
  • which gives a Reference(ServiceRequest.requester)
  • which gives a Reference(Practitioner)