External cause of injury coding: A comparison of the Ninth and Tenth Revisions of International Classification of Diseases

Objective: To contrast the differences in the classification scheme of external cause of injury (ECI) coding between the Tenth and Ninth Revision of International Classification of Diseases (ICD-9 and ICD-10). Methods: We first reviewed the relevant references and then contrasted each code of four main ECI (i.e., land transport, falls, drowning and poisoning) and intent and mechanism matrix between ICD-9 and ICD-10. Results: The ECI was a supplement in ICD-9 and became a formal chapter in ICD-10. The number of 3-digit codes is 372 and 192 in ICD-10 and ICD-9, respectively. Two optional 4 digit codes (i.e., place of injury and activity) were added in ICD-10, which could provide more information on environmental events and circumstances. A matrix classification scheme was used for land transport coding in ICD-10, a complete code should include the road user type (e.g., pedestrian, bicycle, motorcycle or car) of both victim and counterpart. Most of the newly added codes in ICD-10 for falls are elderly-related (e.g., being carried or supported by other persons, involving wheelchair or other furniture). The 4th digit of drowning codes concerned more on activities (e.g., sports, recreations or work related) in ICD-9. Nevertheless, in ICD-10 more information was required regarding to place and circumstances (e.g., bath-tub, swimming pool or natural water). Besides, ICD-10 further classified drowning as 'while in' (e.g., swimming pool) or 'fall into' (e.g., swimming pool), which had different implication for injury prevention. Poisoning was the only main ECI of which the number of codes decreased from ICD-9 to ICD-10. Conclusions: With regard to the classification scheme, ECI in ICD-10 could provide more information on environmental events and circumstances compared with ICD-9. However, the 4th digit-related information was not available in Taiwan because only 3-digit codes were used for ICD-9. The 4-digit codes will be used in Taiwan for ICD-10, the ECI information will be increased.