Validity of the diagnosis of acute myocardial infarction in Korean National Medical Health Insurance claims data: The Korean Heart Study

Background and Objectives: Medical insurance claims (MIC) data are one of the largest sources of outcome data in the form of International Classification of Diseases (ICD) codes. We evaluated the validity of the ICD codes from the Korean National MIC data with respect to the outcomes from acute myocardial infarction (AMI) in the Korean Heart Study. Subjects and Methods: Baseline information was obtained from health examinations conducted from 1994 to 2001. Outcome information regarding the incidence of AMI came from hospital admission discharge records from 1994 to 2007. Structured questionnaires were sent to 98 hospitals. In total, 107 cases of AMI with ICD codes of 121- (93 men, 26-73 years of age) were included in the final analyses. ICD code accuracy and reliability (kappa) for AMI were calculated. Results: A large number of AMI cases were from hospitals located in the Seoul area (75.9%). The accuracy of AMI was 71.4%, according to World Health Organization criteria (1997-2000, n=24, kappa=0.46) and 73.1% according to the European Society of Cardiology/American College of Cardiology (ESC/ACC) criteria (2001-2007, n=83, kappa=0.74). An age of 50 years or older was the only factor related to inaccuracy of codes for AMI (odds ratio, 4.6; 95% confidence interval, 1.2-17.7) in patients diagnosed since January 2001 using ESC/ACC criteria (n=83). Conclusion: The accuracy for diagnosing AMI using the ICD-10 codes in Korean MIC data was >70%, and reliability was fair to good; however, more attention is required for recoding ICD codes in older patients.