Accuracy of injury coding in a Canadian workers compensation system

This study assessed the validity of injury-related diagnostic codes used in a workers compensation claims database using a hospital discharge database as a comparative standard. Hospital discharge records and work ers compensation records were extracted and matched for a cohort of 5,876 sawmill workers in British Columbia. A total of 333 injuries were linked. Of these, 107 injuries matched on the four-digit ICD-9 code (32%), 162 injuries matched on the three-digit code (49%), and 228 injuries matched on the two-digit code (69%). When comparing the nature of injury information between the two records, 232 (70%) injury events matched. The levels of agreement (measured by Kappa values) were good for all injuries (0.64), high for the nature of injury such as burns (0.97), and low for superficial injury/contusion/crushing (0.28). This study supports the use of workers compensation claims databases for occupational epidemiology and injury surveillance investigations.