In Reply We thank Mori et al for their insightful comments and interest in our article.1 The authors argue that although the National Inpatient Sample (NIS) is a powerful tool, the Elixhauser comorbidity index is of poor utility owing to overlap between preoperative comorbidities and postoperative complications.
While we acknowledge this widely accepted limitation of administrative claims databases, it is important to note that this is not limited to the Elixhauser comorbidity index alone. Among available tools, it remains one of the most valid indices used for administrative data. To our knowledge, there are currently no studies to investigate the validity of any of these scores specifically in the setting of cardiac surgery, although studies in other surgical specialties, like orthopedic surgery, endorse the superiority of the Elixhauser comorbidity index.2