Development and validation of a registry-based definition of eosinophilic esophagitis in Denmark

AIM:To develop and validate a case definition of eosinophilic esophagitis(EoE) in the linked Danish health registries.METHODS:For case definition development,we queried the Danish medical registries from 2006-2007 to identify candidate cases of EoE in Northern Denmark.All International Classification of Diseases-10(ICD-10) and prescription codes were obtained,and archived pathology slides were obtained and re-reviewed to determine case status.We used an iterative process to select inclusion/exclusion codes,refine the case definition,and optimize sensitivity and specificity.We then re-queried the registries from 2008-2009 to yield a validation set.The case definition algorithm was applied,and sensitivity and specificity were calculated.RESULTS:Of the 51 and 49 candidate cases identified in both the development and validation sets,21 and 24 had EoE,respectively.Characteristics of EoE cases in the development set [mean age 35 years;76% male;86% dysphagia;103 eosinophils per high-power field(eos/hpf)] were similar to those in the validation set(mean age 42 years;83% male;67% dysphagia;77 eos/hpf).Re-review of archived slides confirmed that the pathology coding for esophageal eosinophilia was correct in greater than 90% of cases.Two registrybased case algorithms based on pathology,ICD-10,and pharmacy codes were successfully generated in the development set,one that was sensitive(90%) and one that was specific(97%).When these algorithms were applied to the validation set,they remained sensitive(88%) and specific(96%).CONCLUSION:Two registry-based definitions,one highly sensitive and one highly specific,were developed and validated for the linked Danish national health databases,making future population-based studies feasible.