Can Eosinophilic Esophagitis be Reliably Diagnosed in Administrative Databases?

Abstract

Purpose: The use of administrative databases to conduct population-based studies of eosinophilic esophagitis (EoE) in the United States is limited by the lack of a validated case definition of EoE. It is unknown whether the ICD-9 code for EoE, 530.13, accurately identifies those who truly have the disease. The goal of this study was to validate the ICD-9 code for identifying cases of EoE in administrative data using patient-level claim reports and medical records. Methods: This was a retrospective study performed at University of North Carolina (UNC). Confirmed cases of EoE as per consensus guidelines (symptoms of esophageal dysfunction and ≥ 15 eos/hpf on biopsy after 8 weeks of twice daily PPI therapy) were identified in the UNC EoE clinicopathologic database from 2008-2010; 2008 was the first year in which the 530.13 code was approved. Using the Carolina Data Warehouse (CDW), a clearing house for claims and administrative data for patients seen in the UNC system, all diagnostic and procedure codes were obtained for these cases. Then, with the EoE cases as the reference standard, we re-queried the CDW over the same time frame for all patients seen in the system (n=308,372) and calculated the sensitivity and specificity of the ICD-9 code 530.13 alone as a case definition of EoE. We repeated this process in an iterative fashion to attempt to refine the case definition by adding or subtracting components to optimize sensitivity and specificity. Results: We identified 226 cases of EoE at UNC to serve as the reference standard for case definition validation. Characteristics of patients with EoE were: mean age 26 yrs (range 6 mo to 82 yrs); 71% male; 77% Caucasian; maximum eosinophil count 63±40 eos/hpf. A case definition using the ICD-9 code 530.13 alone yielded a sensitivity of 37% (83/226; 95% CI: 31-43%) and specificity of 99% (308,111/308,146; 95% CI: 98-100%). These operating parameters were not substantially altered if the case definition required a procedure code for endoscopy or if cases were limited to those with commercial insurance. Conclusion: The ICD-9 code for EoE, 530.13, had only fair sensitivity for identifying cases of EoE in administrative data. However, the specificity of this code was excellent. Use of administrative codes to identify EoE cases will miss over 60% of cases, but those identified in this manner are highly likely to have the disease.