Allergies & Intolerance Use Cases
HL7 Patient Care Technical Committee
Larry McKnight, MD
Use Case 1: Clinical Care of patients
• Allergy lists are entered and reviewed regularly as
a routine part of clinical care.
Entered, revised, updated, and clarified at various points
in time:
Ambulatory H&P
Hospital Admission (nurse/physician/pharmacist)
Need to order medication that conflicts
Random times when patient recall of old allergy after recorded
or new adverse reaction noted.
• May be shared from other clinical information systems.
– HIS to pharmacy
Use Case 1: Clinical Care of patients
• The purpose of capturing allergies is to avoid
inadvertantly giving the patient a therapy that may
cause harm.
The allergy list is used in:
– Clinical reasoning by humans – simple display of information
– Automated decision support – active check during medication
• Provider Order Entry System, Pharmacy, RIS
• Allergy lists typically require explicit negation to show "I
NKDA (drug)
NKFA (food)
Latex (Y/N)
IV Contrast (Y/N)
Use Case 1: Clinical Care of patients
• Typically the important clinically important characteristics to record
are for each allergy are:
Allergen (typically one per allergy) Eg. Penicillin
Reaction (may be many per allergen) Eg. Hives
Severity (of each reaction) Eg. Severe
Onset of allergy in patient. Eg. When did the patient first note it.
Who is asserting it and when. Eg. The clinician
Certainty (see next slide)
Type of Allergen:
• Eg. Food, environment, medication.
• May be required for CDSS to work
– Type of "Allergy"
• Eg. True Allergy vs Intolerance
– Status (eg recoreded in error or inactive)
– Comments
Use Case 1: Clinical Care of patients
• Other important notes about Clinical Allergies
– The allergen is generally only one component of the administered
substance that was temporally associated with the adverse reaction,
and it may be unclear what the actual allergen is. This is usually a
clinical judgment based on and always starts with patient history.
– More certainty may be obtained by specific allergy testing such as
skin testing or checking antibody titers.
– Allergens may cross react.
– Many people use the term to include "intolerance" for any other
reason the patient doesn't want to have a particular medication given.
– There are a relative few common allergens (eg Sulfa, Latex), but
theoretically any substances may be an allergen. Similarly there is a
short list of common reactions, but a very long list of possible reactions
including reactions that require additional constraints such as lighting
(photo erruption).
– Typical patients will have NKDA. 2-3% will have 1 or 2 drug allergies,
but some have >15.
Use Case 1: Clinical Care of Patients
• Examples of Recording and Updating Allergy lists:
– While recording an Admission Assessment, the nurse asks about
what allergies the patient has. The patient says: "penicillin"
The nurse asks about what kind of reaction the patient has. The
patient says " I don't know, my mom told me not to take it when
I was a kid"
– While capturing a history and physical the patient state to the
physician "I think I have a reaction to the '-cillins' – I get a rash"
Use Case 1: Clinical Care of Patients
• More examples:
– While seeing a patient in the Emergency room, the admitting
physician says to the patient "I see from the medical record you
have an allergy to peanuts. What happens when you take
peanuts?". The patient states "My face swells. I've been
hospitalized 3 times for after eating even tiny amounts"
– Doctor needs to order an CT scan, and notices an allergy to IV
contrast recorded. Patient states "I have no idea how that got
there – I just had a CT with IV contrast last month without
Use Case 2: Recording an Allergic
Reaction Event or Adverse Reaction
• A Problem/Diagnosis/Condition/Concern
– Can be used in Reason for visit.
– Followed and tracked independently as a regular "concern"
– Prompts for Further Evaluation and Treatment (eg Epinephrine,
Steroids, Antihistamines)
– May still be mild or severe.
• Examples
Anaphylaxis after a bee sting
Decreased platelets while on Heparin (HIT)
Allergy to peanuts under evaluation
Seasonal allergy (pollen) / Angioedema (ACEI)
• allergen often unknown, unlisted.
• Should result in updated allergy list – if / when allergen
Use Case 3: Allergy Confirmation
• Skin testing
– A controlled observation.
Same assertion model -- just a more controlled environment.
Greater confidence in results -- >85% sens and spec.
Used for food, environment and medications.
Type: Intradermal skin test, patch testing, …
– Contraindications
• Severe reaction based on history
• Always start based on history
– Factors affecting results
• On some other meds – eg. Steroids, antihistamines, …
• Skin conditions
• Do these need to be explicitly listed? (they are not currently in
Use Case 3: Allergy Confirmation
• Supporting results
– Fluorescent enzyme immunoassay and RAST
(Radioallergosorbent Tests)
– Food Challenges.
– Endoscopy.
– Platelet level dropping
– A picture of the rash.
• Simple Observations
– Does this need to be a general Clinical Statement?
Use Case 4: Adverse Reaction
• Allergy assertion is NOT made.
– Simply an observation and recording of a reaction
• Examples:
– Investigational medication with any adverse reaction.