C.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
C.2 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.
The statusCode of the Allergy Concern Act is the definitive indication of the status of the concern, whereas the effectiveTime of the nested Allergy - Intolerance Observation is the definitive indication of whether or not the underlying allergy is resolved.
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).
C.3 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.
The effectiveTime of the Allergy - Intolerance Observation is the definitive indication of whether or not the underlying allergy/intolerance is resolved. If known to be resolved, then an effectiveTime/high would be present. If the date of resolution is not known, then effectiveTime/high will be present with a nullFlavor of "UNK".
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.
C.4 Result Observation (V3)
This template represents the results of a laboratory, radiology, or other study performed on a patient.
The result observation includes a statusCode to allow recording the status of an observation. “Pending” results (e.g., a test has been run but results have not been reported yet) should be represented as “active” ActStatus.
For examples of C-CDA templates, see the C-CDA implementation guide.
C.5 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.
http://www.hl7.org/implement/standards/product_brief.cfm?product_id=308
Figure 7: Patient Care Domain Analysis Model
Selected attribute definitions
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 |
C.6 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.
The IPS includes the following conformance attributes:
M | Mandatory | Shall always be present and - where applicable - shall be instantiated with valid values. No exceptions or empty/null values are allowed in this case. |
|---|---|---|
R | Required | A required element shall always be present and - where applicable - should be instantiated with valid values. Exceptions or empty/null values are allowed in this case. |
RK | Required if Known | If there is information available, the element must be present and - where applicable - instantiated with valid values. If there is no information available, the element may be omitted, may be left empty, or may be instantiated with exceptional or null values depending on the implementation. |
C | Conditional | Depending on predicate conditions, the element may assume different conformance strengths (e.g. O, R, RK) or not being present. |
O | Optional | This data element can be omitted from a derived model, including from implementations. Recipient may ignore optional elements. |
The Allergies and Intolerance section of IPS data set includes:
Data Element | Conformance | Datatype | Data Element Description |
|---|---|---|---|
Allergies/Intolerances content status | C | coded | As this IPS Section is mandatory for conformance, information about “known absence of allergies” or no information about allergies is required to be stated. Known Content will be accompanied by the conditional list of Allergies and intolerances. |
Allergies and Intolerances | C | List | If present then they shall be listed else give explicit reasons for why none are recorded. An ordered list comprising the name, code, a description of the Allergy/intolerance and Agent details for each Allergy/intolerance. |
1) Allergy/Intolerance | M | Label concept | If allergies present then they shall be listed else give explicit reasons for why none are recorded. An ordered list comprising the name, code, a description of the Allergy/intolerance and Agent details for each Allergy/intolerance. |
a. Allergy/Intolerance description | R | Text | Textual description of the allergy or intolerance. |
b. Clinical status | R | Coded | Provides the current status of the allergy or intolerance (e.g., active) |
c. Onset date | RK | Datetime | It shall be provided with the highest known precision, at least to the year |
d. End Date | C | Datetime | If Clinical Status is non-active then an exception can be raised to indicate inconsistency. It shall be provided with the highest known precision, at least to the year. |
e. Criticality | O | Coded | Represents the gravity of the potential risk for future life-threatening adverse reactions when exposed to a substance known to cause an adverse reaction in that individual. |
f. Certainty | O | Coded | Assertion about certainty associated with the propensity, or potential risk, of a reaction to the identified substance. |
g. Type of propensity | RK | Coded | Type of allergy or intolerance. (e.g., allergy) |
h. Diagnosis | O | Coded | A code indicating the type of reaction and the agent; an alternative option for describing an allergy to the agent. (e.g., lactose intolerant) |
i. Reaction | RK | Label Concept | A Label Concept recognizing that other data concerning the reaction may be made available in later versions of this standard. |
i) Manifestation of the reaction | RK | Coded | Description of the clinical manifestation of the allergic reaction. Example: anaphylactic shock |
ii) Severity | RK | Coded | Coded element that describes the subjective assessment of the severity of the condition as evaluated by the clinician, in the case of an allergy it is used as attribute of a manifestation of a reaction. |
j. Agent | R | Label Concept |
|
iii) Agent code | R | Coded | A specific allergen or other agent/substance to which the patient has an adverse reaction propensity. |
iv) Category | O | Coded | Allergy substance category (eg food) |
Additional information about FHIR® implementation guide of the International Patient Summary can be found here: http://hl7.org/fhir/uv/ips/ .
C.7 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).
