In the National Hospital Ambulatory Medical Care Survey (NHAMCS), an emergency department visit for an injury may be classified based on the International Classification of Diseases (ICD–CM) code. In Health, United States, injury visits are presented for initial visits (that is, visits where active care for the injury is provided). Starting with 2016 data, visits are classified according to the International Classification of Diseases, 10th Revision, Clinical Modification (ICD–10–CM). A visit was considered injury-related if the physician diagnosis was injury-related or if an external cause-of-injury code was used. Injury diagnoses include all S codes and select injury diagnosis T codes. External cause-of-injury codes include all V, W, and X codes, Y00–Y38, and select T codes. An injury visit is considered initial if the seventh character of the ICD–10–CM code is A–C or missing. For more information on classifying injury visits, see Hedegaard H, Johnson RL, Garnett MF, Thomas KE. The International Classification of Diseases, 10th Revision, Clinical Modification (ICD–10–CM) external cause-of-injury framework for categorizing mechanism and intent of injury. National Health Statistics Reports; no 136. Hyattsville, MD: National Center for Health Statistics. 2019.
Before 2016 data, diagnosis was classified according to the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD–9–CM). A visit was considered injury-related if the physician diagnosis was injury-related or an external cause-of-injury code was present. In the 2001–2015 NHAMCS, an initial injury visit was the first visit to an emergency department for an injury that was characterized by either the first-listed diagnosis being a valid injury diagnosis or by a valid first-listed external cause-of-injury code, regardless of the diagnosis code. Visits for which the first-listed diagnosis or the first-listed external cause-of-injury code was for a complication of medical care or for an adverse event were not counted as injury visits. For an explanation of the methodology used to create the imputed initial visit variable before 2016, see: http://www.cdc.gov/nchs/data/ahcd/initialvisit.pdf. For more information, see the CDC/NCHS Injury Data, Reports, and Other Resources website at: http://www.cdc.gov/nchs/injury.htm; and Fingerhut LA. Recommended definition of initial injury visits to emergency departments for use with the NHAMCS–ED data. NCHS Health E-Stats. 2006. Available from: http://www.cdc.gov/nchs/data/hestat/injury/injury.htm. (Also see Sources and Definitions, Emergency department or emergency room visit; External cause of injury; Injury; International Classification of Diseases, Clinical Modification [ICD-CM].)