Concordance between childhood injury diagnoses from two sources: an injury surveillance system and a physician billing claims database

Objectives: ( 1) To determine the concordance between injury diagnoses ( head injury ( HI), probable HI, or orthopedic injury) for children visiting an emergency department for an injury using two data sources: an injury surveillance system ( Canadian Hospitals Injury Research and Prevention Program, CHIRPP) and a physician billing claims database ( Regie de l'assurance maladie de Quebec, RAMQ), and ( 2) to determine the sensitivity and specificity of diagnostic and procedure codes in billing claims for identifying HI and orthopedic injury among children. Design: In this cross sectional cohort, data for 3049 children who sought care for an injury ( 2000 - 01) were obtained from both sources and linked using the child's personal health insurance number. Methods: The physician recorded diagnostic codes from CHIRPP were used to categorize the children into three groups ( HI, probable HI, and orthopedic), while an algorithm, using ICD-9-CM diagnostic and procedures codes from the RAMQ, was used to classify children into the same three groups. Results: Concordance between the data sources was substantial'' ( weighted Kappa 0.66; 95% CI 0.63 to 0.69). The sensitivity of diagnostic and procedure codes in the RAMQ database for identifying HI and for orthopedic injury were 0.61 ( 95% CI 0.57 to 0.64) and 0.97 ( 95% CI 0.96 to 0.98), respectively. The specificity for identifying HI and for orthopedic injury were 0.97 ( 95% CI 0.96 to 0.98) and 0.58 ( 95% CI 0.56 to 0.63), respectively. Conclusion: Combining diagnostic and procedures codes in a physician billing claims database ( the RAMQ database) may be a valid method of estimating injury occurrence among children.