Do inadequacies in ICD-10-AM activity coded data lead to underestimates of the population frequency of sports/leisure injuries?

Aims: To assess the use of the International Classification of Diseases Australian Modification (ICD-10-AM) activity sub-codes for identifying sports/leisure injury hospitalizations and the impact of missing codes on population incidence estimates. Methods: Injury-related hospital separations in New South Wales, Australia, for the period 2003-04 were examined with sports/leisure cases identified by the ICD-10-AM activity codes. Results: Over 30% of all injury hospitalizations had either a missing or unspecified activity code. Among cases with valid activity codes, 13.9% of all injury hospitalizations were associated with sports/leisure. When adjusted for underreporting associated with undefined or missing activity codes, sports/leisure injuries accounted for up to 20% of injury hospitalizations. Conclusion: Defining sports/leisure injury cases on the basis of activity codes is likely to lead to an underestimate of their contribution to the overall injury burden. Improvements need to be made to the completeness of activity coding of hospitalization data.C