Expand implicit ValueSet to get all terms having a specific part as ancestor

From the specification “Using LOINC with FHIR”, section “Implicit value sets”, sub-section “Multi-Axial Hierarchy”, I understand that all LOINC terms having part LP31755-9 (Microbiology) should be obtainable through an expand of this implicit value set:


LOINC’s FHIR terminology server returns this result instead:
<div id=“line1”><span class=“hlControl” style=“color: #660000;”>{</span></div>
<div id=“line2”> <span class=“hlTagName” style=“color: #006699;”>“resourceType”</span>: <span class=“hlQuot” style=“color: #8888ff;”>“OperationOutcome”</span><span class=“hlControl” style=“color: #660000;”>,</span></div>
<div id=“line3”> <span class=“hlTagName” style=“color: #006699;”>“issue”</span>: <span class=“hlControl” style=“color: #660000;”>[</span> <span class=“hlControl” style=“color: #660000;”>{</span></div>
<div id=“line4”> <span class=“hlTagName” style=“color: #006699;”>“severity”</span>: <span class=“hlQuot” style=“color: #8888ff;”>“error”</span><span class=“hlControl” style=“color: #660000;”>,</span></div>
<div id=“line5”> <span class=“hlTagName” style=“color: #006699;”>“code”</span>: <span class=“hlQuot” style=“color: #8888ff;”>“processing”</span><span class=“hlControl” style=“color: #660000;”>,</span></div>
<div id=“line6”> <span class=“hlTagName” style=“color: #006699;”>“diagnostics”</span>: <span class=“hlQuot” style=“color: #8888ff;”>“Unknown ValueSet: http%3A%2F%2Floinc.org%2Fvs%2FLP31755-9”</span></div>
<div id=“line7”> <span class=“hlControl” style=“color: #660000;”>}</span> ]</div>
<div id=“line8”><span class=“hlControl” style=“color: #660000;”>}</span></div>
Could you tell me why? Thank you.

Here is a more readable view of the result above:


I apologize for the formatting issues of this forum. I believe this is the readable view you were attempting to post.

  "resourceType": "OperationOutcome",
  "issue": [ {
    "severity": "error",
    "code": "processing",
    "diagnostics": "Unknown ValueSet: http%3A%2F%2Floinc.org%2Fvs%2FLP31755-9"
  } ]

I am working on a reply to your original issue and hope to have it posted here soon.

Hello François,

I see a few potential issues here. The first is with regard to the functionality specified by HL7 at https://www.hl7.org/fhir/loinc.html. The ValueSet for Multi-Axial Hierarchy entries ( http://loinc.org/vs/[partcode] ) is not available within LOINC’s Terminology Service (TS) using FHIR, fhir.loinc.org. Our TS uses SmileCDR (HAPI-FHIR) and this functionality does not seem to be implemented here.

Also, the Part code you provided ( LP31755-9 ) is not an entry in LOINC’s Multi-Axial Hierarchy (MAH). It is a Component Part for Microbiology. The MAH Part for Microbiology is LP7819-8. You can get this Part’s parent/child relationships at:


However, this does not provide what I believe you want: LOINC codes for microbiology lab tests. I do not think this is presently available through a programmatic means.

I tried using a filtered expansion of the implicit value set but this does not provide the desired result.


Perhaps I have the syntax wrong and someone else can provide us some insight. Until then, you can retrieve and export a list of micro terms via SearchLOINC. I realize this is not the same as an API request but I hope it will help until we resolve the issue of the missing MAH Part value sets.


Best regards,

Thank you Tim, for the 3 issues explained.