Coding Disparity and Specificity during Emergency Department Visits after Transitioning to the Tenth Version of the International Classification of Diseases

The purpose of this study was to examine coding changes using the International Classification of Diseases (ICD) after the transition from ICD-9 to ICD-10. We studied a national cohort of emergency department visits from the Veterans Health Administration (VHA) before and after the transition, focusing on coding disparity and coding specificity. The cohort accounted for 2 million emergency department visits by 1.2 million patients. There were no statistical differences between the groups with respect to demographics, comorbidities, diagnoses, or use of medical services. While ICD-10 offered significantly more codes as well as more specific coding options, the ICD-10 encounters continued to use a small number of codes, were less likely to use multiple codes, and did not consistently exploit the more unique codes to create more specific diagnoses. These findings within the VHA system corresponded to similar challenges that have been documented with Medicare claims and in the private sector.