Mapping hypersensitivity/allergic diseases in the International Classification of Diseases (ICD)-11: cross-linking terms and unmet needs

BACKGROUND With the aim of actively contributing to the ongoing 11(th) International Classification of Diseases (ICD) revision, an international collaboration led by the European Academy of Allergy and Clinical Immunology (EAACI) has decided to revise the classification of hypersensitivity/allergic diseases and to validate it for ICD-11 by crowdsourcing the allergist community. However, understanding that the construction of a classification was necessary but not sufficient, we developed a mapping strategy in the attempt to better fit it to the ICD-11 linearization structure. METHODS The cross-linking terms process has been constructed based on an algorithm in which we prioritized the pre-coordination, followed by the post-coordination when the first step was not possible. If the above strategies failed to identify the entries, the conditions were ruled as "non specific terms", "no code fit properly" or "missing terms". RESULTS Amongst the 652 terms distributed in 5 main groups of the Hypersensitivity/Allergic Diseases classification, 169 terms fit directly the codes listed in the ICD-11 beta draft (October 2014 version), 26 were considered as "nonspecific term", 21 were linked to the Foundation by Index, 7 were recorded as inclusions and 2 were cited just in the definition of the condition. The post-coordination was possible for 97 terms, mainly for drug hypersensitivity conditions. We noticed a considerable number of allergen references missing. CONCLUSION The proposed strategy of cross-linking terms and the results of this process can actively contribute to updating the hypersensitivity and allergic conditions classification in the ICD-11 beta revision and underlines the need for either a new chapter in ICD-11 possibly entitled Hypersensitivity / Allergic Disorders or at the very least the aggregation of all such diseases under the "Diseases of Immune System" chapter in order for the overlaps to be double parented to the appropriate 'system' chapters.