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1.1.1 HL7 C-CDA model
The Consolidated Clinical Document Architecture (C-CDA) specification (release 1.1 and 2.0) is required for communication of clinical data at transitions of care by the Office of the National Coordinator (ONC) for Health IT in the US. The ONC 2015 Edition Final Rule updated this requirement to specify the 2.1 version for Meaningful Use Stage 3 certification. The 2.1 C-CDA version includes an updated Allergy - Intolerance Observation (V2) 2.16.840.1.113883.10.20.22.4.7 template which includes a new Criticality Observation 2.16.840.1.113883.10.20.22.4.145 (replacing the previous Severity Observation (V2) at the allergy propensity level – the Severity Observation (V2) continues to be used in the Reaction Observation (V2)). The other relevant templates for use cases in section 3 are: Allergy Concern Act (V3) 2.16.840.1.113883.10.20.22.4.30 and Result Observation (V2) 2.16.840.1.113883.10.20.22.4.2.
The latest information about the HL7® C-CDA® standard can be found here: http://www.hl7.org/implement/standards/product_brief.cfm?product_id=492
1.1.1.1 Allergy Concern Act (V3)
This template reflects an ongoing concern on behalf of the provider that placed the allergy on a patient’s allergy list. As long as the underlying condition is of concern to the provider (i.e., as long as the allergy, whether active or resolved, is of ongoing concern and interest to the provider), the statusCode is “active”. Only when the underlying allergy is no longer of concern is the statusCode set to “completed”. The effectiveTime reflects the time that the underlying allergy was felt to be a concern.
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The effectiveTime/low of the Allergy Concern Act asserts when the concern became active. This equates to the time the concern was authored in the patient's chart. The effectiveTime/high asserts when the concern was completed (e.g., when the clinician deemed there is no longer any need to track the underlying condition).
1.1.1.2 Allergy - Intolerance Observation (V2)
This template reflects a discrete observation about a patient's allergy or intolerance. Because it is a discrete observation, it will have a statusCode of "completed". The effectiveTime, also referred to as the "biologically relevant time" is the time at which the observation holds for the patient. For a provider seeing a patient in the clinic today, observing a history of penicillin allergy that developed five years ago, the effectiveTime is five years ago.
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The agent responsible for an allergy or adverse reaction is not always a manufactured material (for example, food allergies), nor is it necessarily consumed. The following constraints reflect limitations in the base CDA R2 specification, and should be used to represent any type of responsible agent, i.e., use playingEntity classCode = "MMAT" for all agents, manufactured or not.
1.1.1.3 Result Observation (V3)
This template represents the results of a laboratory, radiology, or other study performed on a patient.
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For examples of C-CDA templates, see the C-CDA implementation guide.
1.1.2 HL7 Patient Care Domain Analysis Model
This domain analysis model for allergy records was developed by the HL7 Patient Care Work Group and has been used to inform the allergy/intolerance modeling in the C-CDA® and FHIR® specifications.
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Attribute name | Datatype | Definition |
Adverse reaction | ||
severity | Coded | Assessment of the severity of the reaction |
didNotOccurFlag | Boolean | Indicates a reaction did not occur at contact with substance |
OccurrenceDate | DateTime | Time stamp for manifestation of the reaction |
Health condition | ||
status | Coded | Current status of the concern |
Adverse sensitivity to substance | ||
criticality | Coded | Clinical judgement regarding potential seriousness of a future reaction. |
sensitivityType | Coded | Allergy; intolerance |
createdDate | Date Time | Date time the entry was created |
Substance | ||
identifier | Coded | Coded reference to the substance involved in the reaction |
name | String | Name of the substance |
Exposure | ||
exposureDate | Date Time | Date time when the exposure occurred; may be approximated |
exposureType | Coded | How the exposure occurred, eg vaccination, prescription, administration, accidental |
Manifestation | ||
severity | Coded | Severity of the manifestation of the reaction |
reactionType | Coded | Clinical finding characterizing the reaction, eg code for rash or hives |
Sensitivity test | ||
identifier | Identifier | Identifier pointing to results of the sensitivity test |
name | String | Name of the test |
1.1.3 Fast Healthcare Interoperability Resources (FHIR®; HL7®)
FHIR® is an HL7® standard for exchanging healthcare information electronically. The fourth STU release (R4) was published in October 2019, including the first (partial) normative content. FHIR models the classes of information for interoperable use as Resources. The FHIR® Resources relevant to the use cases in section 4 are AllergyIntolerance, Condition and Observation.
1.1.3.1 AllergyIntolerance resource
The full resource model structure, coded elements and terminology bindings of the AllergyIntolerance resource can be found at http://www.hl7.org/fhir/allergyintolerance.html, with various display options, including UML, XML, JSON, Turtle and the differences it underwent compared to the prior release(s).
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- When FHIR® R5 is released (expected in late 2022):
- The reaction.manifestation element should be able to directly reference a FHIR Observation resource representing the manifestation (proposal to be balloted in R5). This will allow the manifestation of an adverse reaction to be recorded only once, not first in an Observation resource and then once again in the AllergyIntolerance resource.
- The AllergyIntolerance.type element will have a "CodeableConcept" data type and a binding strength of "Preferred", thus allowing the use of SNOMED CT concepts as values without the use of an extension.
1.1.3.2 Observation resource
The full resource model structure, coded elements and terminology bindings of the Observation resource can be found on http://www.hl7.org/fhir/observation.html, with various display options, including UML, XML, JSON, Turtle and the differences it underwent compared to the prior release(s).
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Path/Element | Definition | Values | Binding Strength | Binding |
Observation.status | The status of the result value. | - registered - preliminary - final - amended - corrected - cancelled - entered in error - unknown | ||
Observation.category | A code that classifies the general type of observation being made. | |||
Observation.code | Type of observation (code / type). Describes what was observed. Sometimes this is called the observation "name". | |||
Observation.dataAbsentReason | Provides a reason why the expected value in the element Observation.value[x] is missing. | |||
Observation.interpretation | A categorical assessment of an observation value. For example, high, low, normal. | |||
Observation.bodySite | Indicates the site on the subject's body where the observation was made (i.e. the target site). May include laterality. | |||
Observation.method | Indicates the mechanism used to perform the observation. | |||
Observation.referenceRange.type | Codes to indicate the what part of the targeted reference population it applies to. For example, the normal or therapeutic range. | |||
Observation.referenceRange.appliesTo | Codes to indicate the target population this reference range applies to. For example, a reference range may be based on the normal population or a particular sex or race. | |||
Observation.component.code | Type of component observation (code / type). | |||
Observation.component.dataAbsentreason | Provides a reason why the expected value in the element Observation.component.value[x] is missing. | |||
Observation.component.interpretation | A categorical assessment of an observation value. For example, high, low, normal. |
1.1.3.3 Condition resource
The resource model structure, coded elements and terminology bindings of the Condition resource can be found on http://www.hl7.org/fhir/condition.html, with various display options, including UML, XML, JSON, Turtle and the differences it underwent compared to the prior release(s).
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Path/Element | Definition | Values | Binding Strength | Binding |
Condition.clinicalStatus | The clinical status of the condition or diagnosis. | - active - recurrence - relapse - inactive - remission - resolved | ||
Condition.verificationStatus | The verification status to support or decline the clinical status of the condition or diagnosis. | - unconfirmed - provisional - differential - confirmed - refuted - entered-in-error | ||
Condition.category | A category assigned to the condition. | |||
Condition.severity | A subjective assessment of the severity of the condition as evaluated by the clinician. | |||
Condition.code | Identification of the condition or diagnosis. | |||
Condition.bodySite | Codes describing anatomical locations. May include laterality. | |||
Condition.stage.summary | Codes describing condition stages (e.g. Cancer stages). | |||
Condition.stage.type | Codes describing the kind of condition staging (e.g. clinical or pathological). | |||
Condition.evidence.code | Codes that describe the manifestation or symptoms of a condition. |
1.1.3.4 Example of a typical Medication allergy resource from a clinical system (id = "medication") (JSON format):
| Code Block |
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{
"resourceType": "AllergyIntolerance",
"id": "medication",
"text": {
"status": "generated",
"div": "<div xmlns=\"http://www.w3.org/1999/xhtml\"><p><b>Generated Narrative with Details</b></p><p><b>id</b>: medication</p><p><b>clinicalStatus</b>: Active <span>(Details : {http://terminology.hl7.org/CodeSystem/allergyintolerance-clinical code 'active' = 'Active', given as 'Active'})</span></p><p><b>verificationStatus</b>: Unconfirmed <span>(Details : {http://terminology.hl7.org/CodeSystem/allergyintolerance-verification code 'unconfirmed' = 'Unconfirmed', given as 'Unconfirmed'})</span></p><p><b>category</b>: medication</p><p><b>criticality</b>: high</p><p><b>code</b>: Penicillin G <span>(Details : {RxNorm code '7980' = 'Penicillin G', given as 'Penicillin G'})</span></p><p><b>patient</b>: <a>Patient/example</a></p><p><b>recordedDate</b>: 01/03/2010</p><p><b>recorder</b>: <a>Practitioner/13</a></p><h3>Reactions</h3><table><tr><td>-</td><td><b>Manifestation</b></td></tr><tr><td>*</td><td>Hives <span>(Details : {SNOMED CT code '247472004' = 'Weal', given as 'Hives'})</span></td></tr></table></div>"
},
"clinicalStatus": {
"coding": [
{
"system": "http://terminology.hl7.org/CodeSystem/allergyintolerance-clinical",
"code": "active",
"display": "Active"
}
]
},
"verificationStatus": {
"coding": [
{
"system": "http://terminology.hl7.org/CodeSystem/allergyintolerance-verification",
"code": "unconfirmed",
"display": "Unconfirmed"
}
]
},
"category": [
"medication"
],
"criticality": "high",
"code": {
"coding": [
{
"system": "http://www.nlm.nih.gov/research/umls/rxnorm",
"code": "7980",
"display": "Penicillin G"
}
]
},
"patient": {
"reference": "Patient/example"
},
"recordedDate": "2010-03-01",
"recorder": {
"reference": "Practitioner/13"
},
"reaction": [
{
"manifestation": [
{
"coding": [
{
"system": "http://snomed.info/sct",
"code": "247472004",
"display": "Hives"
}
]
}
]
}
]
} |
1.1.3.5 Using SNOMED CT concepts in FHIR® resources
The SNOMED on FHIR group can provide help and direction on how to deal with the specific issues that may arise when using SNOMED CT concepts in FHIR® resources. SNOMED CT implementation in FHIR guidance can be found here: http://build.fhir.org/ig/IHTSDO/snomed-ig/, while proposals of SNOMED CT adapted FHIR resources can be found here: http://build.fhir.org/ig/IHTSDO/snomed-ig/profiles.html.
You will note that there are two separate FHIR® profiles proposed on this page, based on the general HL7 FHIR AllergyIntolerance resource. One is substance-focused, meaning that the record centers for the AllergyIntolerance.code value on the substance the patient reacts to and captures separately the type of reaction in the AllergyIntolerance.type element. One can say this model captures the allergy/intolerance to X in a post-coordinated way. The second profile is finding-focused, meaning it captures the allergy/intolerance in the AllergyIntolerance.code element using pre-coordinated "allergy/intolerance to X" SNOMED CT concepts and makes no use of the AllergyIntolerance.type element.
1.1.4 ISO International Patient Summary (IPS)
The IPS is designed to provide clinical information to assist care across any jurisdictional (e.g. local, regional, state/provincial, national) or organizational border by providing a minimal but not exhaustive data set useful for subsequent clinical care scenarios. It emphasizes the data required and the associated business rules to support use and the necessary conformance of the use case for an international patient summary. The ISO TC215 International Patient Summary includes a section on Allergies and Intolerances.
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Additional information about FHIR® implementation guide of the International Patient Summary can be found here: http://hl7.org/fhir/uv/ips/ .
1.1.5 Other information models
There were other published allergy and hypersensitivity information models being considered at the initial drafting of this document in 2014, which included epSOS, openEHR, US Federal Health Information Model and UK NHS Connecting for Health Information Model. Their analysis fed into the creation of the inclusive model. Since then, HL7®-related information models, especially FHIR®, have become increasingly popular. Therefore, this document focuses more on these models. The analyses of the other models can be found in the Appendix. Note that the information may not be up-to-date, and some of the projects which created the models may no longer be active (e.g. the epSOS project concluded in 2014).
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