Renee L. Johnson, M.S.P.H., R.P.T.,¹ Holly Hedegaard, M.D., M.S.P.H.,² Emilia Pasalic, MPH,¹ Pedro Martinez, MPH¹

¹National Center for Injury Prevention and Control

²National Center for Health Statistics

Disclaimer: The findings and conclusions in this blog are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention.

Injury epidemiologists live in a world of standard coding schemas, case definitions, and agreed-upon ways of grouping and categorizing injuries. But what happens when the basic foundation for this type of work undergoes a major change? For decades, injury epidemiologists in the United States and elsewhere relied on the International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) to identify and categorize injuries seen in hospitals and emergency departments. In 2015, a new coding rubric went into effect in the United States. The Department of Health and Human Services (HHS) required all hospitals and health care providers in the United States to use the International Classification of Diseases, 10^th Revision, Clinical Modification (ICD-10-CM) to report electronic health care transactions beginning in October 2015. This change required an update to injury surveillance case definitions, analysis guidance, and standard tools that had been developed for use with ICD-9-CM-coded data to the new “language” of ICD-10-CM.

One might think this shouldn’t be too difficult, but in reality, the transition required a huge effort involving multiple partnerships. The first phase began more than a decade ago when development for tools such as  proposed case definitions and proposed groupings for categorizing injuries by external cause or by injury diagnosis began in the absence of any ICD-10-CM coded data. The approach used in these early efforts was to mirror or update the well-established ICD-9-CM-based tools that were already in place.

Beginning in 2016, injury epidemiologists began to have access to ICD-10-CM-coded hospital and emergency department discharge data. Analysis of these data provided the first opportunity to test the proposed tools and to learn what worked, what didn’t work, and what adjustments needed to be made. Collaborative partnerships among national, state, and local public health agencies; universities; and professional and non-profit organizations worked together to test and refine these tools.  The tools were adjusted based on the test findings and produced:

• final case definitions,
• an ICD-10-CM external cause matrix for categorizing injuries by mechanism and intent, and
• an ICD-10-CM injury diagnosis matrix for categorizing injuries by body region and nature of injury.

In addition to this collaborative work, individual researchers began to study and learn more about how to use ICD-10-CM coded hospital and emergency department discharge data for injury surveillance. Several of these studies have been recently published in a supplemental issue of Injury Prevention titled ICD-10-CM Injury Epidemiology and Surveillance Methods. These studies help clarify methodological considerations when using ICD-10-CM coded data and provide information to support decision-making for developing surveillance case definitions for subcategories of injuries.

The studies cover a broad range of injury topics, including general injury, drug overdose, unintentional falls, intentional self-harm, violence, child abuse and neglect, traumatic brain injury, and work-related injury, and encompass a variety of study methodologies. For example, several studies identified considerations for understanding injury trends and discontinuities across the transition, while other studies utilized medical chart review to estimate the positive predictive value of ICD-10-CM codes and new standardized case definitions. Each of the studies presented in the supplement provides a glimpse into the challenges and the potential of using ICD-10-CM-coded data for injury surveillance.

We encourage you to review the studies in the supplemental issue, whether or not you use ICD-10-CM in your work. The papers provide  examples of methods and lessons learned that can be applied to the implementation of any new health data coding scheme. We hope that this these studies will inspire and provide useful approaches for injury epidemiologists who will be working on the upcoming transition from ICD-10 to the International Classification of Diseases 11^th Revision (ICD-11) for mortality and morbidity data.

For those of you who use ICD-10-CM coded data, we look forward to hearing about your experience and seeing how the use of ICD-10-CM coded data can increase our understanding of injury and injury prevention efforts. Please keep us posted in the comments below with what you learn!