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The FHIR AllergyIntolerence base resource is open to various choices of representation for the adverse sensitivity content per se, but often has restricted ways of providing qualifiers and modifiers.

Adverse sensitivity content value sets

The FHIR AllergyIntolerance base resource has example bindings to SNOMED CT for the element AllergyIntolerance.code as well as elements reaction.substance, reaction.manifestation, and reaction.exposureRoute. All example value sets are though very broad and likely not very precise in determining the set of relevant concepts, see table below. For each data element, the number of concepts that are in the Global Patient Set (GPS) is shown here. The GPS is a special SNOMED CT subset that can be used globally with minimal restriction and at no cost.

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Qualifier and/or modifier value sets

As a result of a request from HL7 to SNOMED International about the possibility of mapping some of the required HL7® FHIR® Value Sets to SNOMED CT, an analysis of the ability of SNOMED CT to accommodate those needs was performed by the SNOMED CT on FHIR Workgroup. The required value sets of the FHIR AllergyIntolerance resource was included in this analysis.

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In the analysis of the FHIR AllergyIntolerance required value sets, all but two were problematic in at least some way. The two straightforward mappable value sets were for elements AllergyIntolerance.reaction.severity and AllergyIntolerance.type

AllergyIntolerance.Reaction.Severity

It was assessed that there was a good match between the HL7 required value set and the SNOMED CT << 272141005 |Severities (qualifier value)| subhierarchy.

AllergyIntolerance.Type

The group's suggested approach here is to use concepts taken from <<609433001 |Hypersensitivity disposition (finding)|unless an actual immune mediated hypersensitivity has been proven e.g., by testing. See section 6.1.1 Allergy list for a further discussion of the rationale behind this approach.

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