Development of a code system for allergens and its integration into the HL7 FHIR AllergyIntolerance resource

Background: Allergy code systems are essential for safety and medical information interoperability. However, current terminology systems lack allergens unique to Japan.

Objective: This study established a code system encompassing Japanese food and non-food/non-medication allergens (JFAGY), and developed a meta-code system for integration with existing drug code systems. The practicality and limitations of the JFAGY were assessed by profiling HL7 FHIR allergy intolerance.

Methods: Allergen terms were selected based on the Standard Commodity Classification of Japan. Additional terms were extracted from clinical guidelines and public documents. For non-food, non-medication allergens, terms from the clinical guidelines were manually compiled to conform to a classification hierarchy. To validate the coverage of the developed food allergen code system, we extracted 823 unique food allergens, totaling 12,027 entries, from two years of electronic health records (EHRs) and performed manual mapping to the code system.

Results: In total, 1,123 food and 607 non-food/non-medication allergen terms were included. The three-digit meta-code system comprises an identifier for coding systems, code length, and allergen categories. The codes allowed the determination of hierarchical relationships between any two terms. The Japanese allergy intolerance value set was developed and bound to the allergy intolerance code. Of the food allergens extracted from EHRs, 62.9% corresponded to unique codes, 6.1% to multiple codes, and 31.0% were unmapped, accounting for 91.5%, 1.9%, and 6.6% of entries, respectively.

Conclusions: The JFAGY encompasses Japanese-specific food and non-food/non-medication allergens, enabling hierarchy determination between two terms, and playing a critical role in medical safety. When utilizing the JFAGY with the FHIR allergy intolerance resource, an FHIR extension must be included to denote a denied allergy.