ICD-9 to ICD-10: evolution, revolution, and current debates in the United States.

The International Statistical Classification of Diseases and Related Health Problems (ICD) has undergone a long evolution from its initial inception in the late 18th century. Today, ICD is the internationally recognized classification that helps clinicians, policy makers, and patients to navigate, understand, and compare healthcare systems and services. Currently in the United States, hot debates surround the transition from the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) to the International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM). This article presents an analysis of the views of the proponents and opponents of the upcoming change. We also briefly present and analyze the quality of the most frequently cited scientific evidence that underpins the recent debates focusing on two major issues: ICD-10-CM implementation costs and revenue gains and the projected clinical data quality improvement. We conclude with policy and research suggestions for healthcare stakeholders.