1. Drug Allergy Substance List
HL7 Patient Care & Vocabulary Work Groups
Saved 26-Apr-17

2. Problem Allergy substances are recorded in many different ways.
A patient’s record may be difficult to read due to redundant records.
Order check rules may not recognize relevant values.
Existing specifications provide very broad guidance.
They don’t support a usable human interface.
Message validation is not feasible.

3. Goal
Produce a relatively concise list of medications (substances, classes, & mixtures) frequently used in allergy & intolerance lists.
Note that the use case is patient safety, not pharmacovigilance. 
This list will support the use of common elements for data capture and validation of exchanged data.
This list is not intended to prevent the recording of unusual substances where necessary, whether by code or text.
We would like to provide a set of standard coded identifiers for these substances. The desiderata for such codes (in addition to semantic accuracy) would be free of charge, readily available, and accepted for use by international stakeholders.

4. Data: Allergy Records VA, Dutch data pending Cerner DoD IMHC KP NE
Cerner
DoD
IMHC KP NE
total
[unassigned]
297,392
7,433
30,153
38,470
5,384
378,832
biologic
4,646
102
1,341
6,089
environmental
1,034,189
28,447
76,114
139,709
4,319
1,282,778
food
1,582,115
58,643
69,437
379,131
4,621
2,093,947
medication
16,333,129
509,605
517,802
3,131,045
107,267
20,598,848
medication class
6,157,854
287,107
237,751
1,140,079
29,081
7,851,872
negation
32,447,511
1,874,531
3,318,006
1,999,170 5
39,639,223
Null
60,058
87,815
9,322
1,115
158,310
supply
1,126,985
818
27,677
116,997
4,971
1,277,448
vaccine
207,981
7,006
7,403
41,039
919
264,348
59,251,860
2,861,405
4,284,445
6,996,303
157,682
73,551,695
VA, Dutch data pending

5. Data: Medication & Class Allergy Records
Source
Substance Strings
Records,
Cerner
10,069
22,492,668
DoD
7,127
796,712
IMHC
1,613
755,553 KP
2,370
4,272,440 NE
1,541
136,348
Aggregate
12,270
28,453,721

6. Term Frequency & Incidence

7. Mapping Threshold 28,453,721 records for medication & medication class

8. Map Questions: Unclassified Strings

9. Top 20 by Institution
Trial mapping

10. Mapping Salts Substance Count Category mapName mapCode mapSystem
mapSource
QAstatus
Abacavir
2733
medication
abacavir
190521
RxNorm
DoD - outbound CHDR
0 - raw
911
IMHC
KP - HL
SNOMED CT
Cerner
ABACAVIR SULFATE
409
abacavir sulfate
221052

11. Issues Mapping unclassified strings Salts
Identify a threshold for effort
Most items below the threshold are unclear anyway
Salts
Is one answer right for all salts?
For all “precise ingredient” refinements?
Boundaries with herbals, vitamins
Vaccines, Biologics
CVX seems too specific
RxNorm offers some more generic vaccine substances, but they are not connected to products
What are likely reactive components – organism markers or stabilizers, preservatives, & adjuvants?
How to handle other biologics – blood, TNF

12. Class issues
Which ones are real & which are not; how to handle exclusions
E.g., Iodine & contrast media
If these are cross-reactive classes, do we also need more specific members?
Pencillins / Pen G
NSAIDS / Acetaminophen
Opiates / Codeine
Salicylate / Aspirin
How are classes to be defined?
ATC/NDF enumeration
SNOMED CT concept
Other approach

13. Class Options SNOMED CT: model in flux NDF-RT, ATC NDF-RT
Classes based on principles that may not align with cross-reactivity
NDF-RT
Many class definitions, all constrained to enumerations, which differ ->
New classes based on cross-reactivity

14. Quality assurance
Caveat: this work is not to be used to map clinical records, and should have no direct effect on any patient. Its sole purpose is to identify frequently used concepts to facilitate information capture.
Issues
Dirty data: ignore ambiguous items and items below threshold
Inconsistent reporting of negatives: partition negative analysis
Duplication: assume duplicates are randomly distributed
Divergent population sizes: compare contributor profiles to identify specific issues, but do not weight incidence
Process
For each string, if count(maps) > 1 and all maps agree, status = OK
If count(maps) < 2, acquire more maps
If maps disagree, review

15. QA Example 5 maps for term RxNorm for this map Don’t use salt Typo
Agreement on map
UMLS for some maps

16. System Options System Substance Class Mixture Realm License SNOMED CT
Yes
Only for products
International
Required
RxNorm No US
Free
UNII
NDF-RT
Possible
ATC
INN*
TBD
*No identified source for INN