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1.22.1.3 Using LOINC with FHIR

1.22.1.3.1 Summary

Source LOINC is made available by the Regenstrief Institute at http://loinc.org
System The URI http://loinc.org identifies LOINC codes
Version Where a version is used, it should be the standard LOINC version e.g. 2.48
Code The LOINC Code Identifier e.g. 21176-3. LOINC codes are not case sensitive
Display Use either the SHORTNAME or LONG_COMMON_NAME field for the display
Filter Properties Several properties are defined as described below

1.22.1.3.2 Copyright Issues

The terms of use for LOINC require that a notice be included with any use of LOINC codes. This notice must appear in the copyright element of any value set that includes LOINC codes (either in the code or filter elements, or in an expansion): 

<copyright value="This content LOINC® is copyright © 1995 Regenstrief Institute, Inc. and the LOINC Committee, and available at no cost under the license at http://loinc.org/terms-of-use"/>

Additional copyright statements may also be found in the copyright element. Some LOINC codes have 3rd party copyright statements. When these codes are included in a value set, they must carry their own copyright statement, using the extension http://hl7.org/fhir/tools/Profile/extensions#copyright .

1.22.1.3.3 Case Sensitivity

For comparison purposes, LOINC codes and values are not case sensitive, though implementers SHOULD maintain the correct case when using LOINC codes and property values.

1.22.1.3.4 Use of LOINC PARTS

As described in the LOINC Manual section 10.2, LOINC Parts are a coded representation of a value for a dimension used to specify a LOINC Term which are assigned a non-semantic identifier with a “LP” prefix and a mod-10 check digit. Following the LOINC license, these part codes may be used in the following ways:

Part codes are the same LOINC URI (http://loinc.org), and SHALL be represented in uppercase (e.g. LP31755-9).

1.22.1.3.5 LOINC Filter Properties

This section documents the property filters that can be used with the LOINC code system in value set composition statements.

1.22.1.3.5.1 LOINC Property filter

Description Allows the selection of a set of LOINC codes with a common property value
Property Name One of the names listed in the "Field Name" column in LOINC Database Structure (Appendix A of the LOINC manual)
Operations Allowed = / regex
Values Allowed [string value]
Comments The 6 properties COMPONENT, PROPERTY, TIME_ASPCT, SYSTEM, SCALE_TYP, and METHOD_TYP are most likely to be useful.

1.22.1.3.5.2 3rd Party Copyright

Description Allows for the inclusion or exclusion of LOINC codes that include 3rd party copyright notices
Property Name copyright
Operations Allowed =
Values Allowed LOINC | 3rdParty | All
Comments LOINC = only codes with a sole copyright by Regenstrief. 3rdParty = only codes with a 3rd party copyright in addition to the one from Regenstrief.

1.22.1.3.5.3 Multi-Axial Hierarchy

Description Allows for the selection of a set of codes base on their appearance in the LOINC multi-axial hierarchy
Property Name parent | ancestor
Operations Allowed = / in
Values Allowed Part Code (or, for "in", multiple part codes separated by commas)
Comments "parent" selects immediate parents only. For example, the code "44022-2" has the parent "LP52960-9". Ancestor includes parents transitively, e.g. "LP52960-9" eventually has a parent "LP31755-9", so the code "44022-2" is in the set of codes that have ancestor=LP31755-9

TODO: Document Ontology

1.22.1.3.6 Implicit Value Sets

Implicit value sets are those whose specification can predicted based on the grammar of the underlying code system, and the known structure of the URL that refers to them. LOINC defines one sets of implicit value sets: By Multi-Axial Hierarchy Entry.

If any value set resources exist with an identifier that conforms to the URL patterns specified below, the content of the resource must conform to the template provided. Profiles and other value set references are allowed to reference these value sets directly. todo: can LOINC actually host a service that returns these?

The value set identifier http://loinc.org/vs is a value set that contains all LOINC codes.

1.22.1.3.6.1 Multi-Axial Hierarchy Entry

A value set with an identifier of "http://loinc.org/vs/[partcode]" must conform to this template, where [partcode] is a part code from the multi-axial hierarchy: 

<ValueSet xmlns="http://hl7.org/fhir">
  <text>
    <status value="generated"/>
    <div xmlns="http://www.w3.org/1999/xhtml">
      [some html that identifies that this value set 
      includes all LOINC codes subsumed by the identified 
      Multi-Axial Heirarchy Part Code]
    </div>
  </text>
  <identifier value="http://loinc.org/vs/[partcode]"/>
  <version value="[optional - but strongly recommended - LOINC version]"/>
  <name value="LOINC Value Set from Multi-Axial Heirarchy code [partcode]"/>
  <description value="All LOINC codes for [partcode or name]"/>
  <status value="active"/>
  <date value="[optional date of LOINC release]"/>
  <compose>
    <include>
      <system value="http://loinc.org"/>
      <filter>
        <property value="ancestor"/>
        <op value="="/>
        <value value="[partcode]"/>
      </filter>
    </include>
  </compose>
</ValueSet>