Predictive value of acute coronary syndrome discharge diagnoses in the Danish national patioent registry

Background: Updated data on the predictive value of acute coronary syndrome (ACS) diagnoses, including unstable angina pectoris, myocardial infarction and cardiac arrest, in hospital discharge registries are sparse. Design: Validation study. Methods: All first-time ACS diagnoses in the Danish National Patient Registry were identified among participants in the Danish cohort study "Diet, Cancer and Health" until the end of 2003. Medical records were retrieved and reviewed using current European Society of Cardiology criteria for ACS. Results: We retrieved medical records from 1577/1654 patients (95.3%) registered with a first-time ACS diagnosis. The overall positive predictive value for ACS was 65.4% (95% confidence interval (CI) 62.9 - 67.7%). Stratification by subdiagnoses and hospital department showed significantly higher positive predictive values for myocardial infarction diagnoses (81.9%; 95% CI 79.5 - 84.2%) and among patients diagnosed with an ACS diagnosis from a ward (80.1%;  95% CI 77.7 - 82.3%), respectively. Conclusion: The ACS diagnoses in hospital discharge registries should be used with caution. If validation is not possible, restricting analyses to patients with myocardial infarctionand/or patients discharged from wards may be a useful alternative.