Accuracy of angina pectoris and acute coronary syndrome in the Danish National Patient Register.

INTRODUCTION: The Danish National Patient Register (DNPR)is widely used for research and administrative purposes. However, its usability is highly dependent of the validity of the registered data. We therefore aimed to determine the positive predictive value (PPV) of angina pectoris and acute coronary syndrome (ACS) in the DNPR. METHODS: We selected a random sample of 500 patients registered with angina pectoris and a random sample of 500 patients registered with ACS among all hospitalisations at any department in Northern Denmark between 1 January 2007 and 31 December 2007. We reviewed the medical records of the sample patients and recorded whether the angina pectoris and the ACS diagnoses were valid, based on the European Society of Cardiology criteria. RESULTS: The PPV of definite and probable angina pectoris was 45.9% (95% confidence interval (CI): 41.3-50.6%), whereas the PPV of verified ACS was 86.6% (95% CI: 83.3-89.5%). Stratification by hospital department revealed significantly higher PPVs for diagnoses received in a cardiology unit for both angina pectoris (61.7%; 95% CI: 53.4-69.6%) and ACS (95.5%; 95% CI: 91.3-98.0%). Stratification by gender showed a significantly higher PPV among men registered with angina pectoris (51.2%; 95% CI: 45.3-57.1%). CONCLUSIONS: The angina pectoris and ACS data contained in the DNPR should be used with caution in register studies if validation is not possible. Restricting analyses of ACS data to patients discharged from cardiology wards may be a useful option in register-based studies. FUNDING: none. TRIAL REGISTRATION: not relevant.

Unrecognised myocardial infarction in patients with schizophrenia.

OBJECTIVE: Schizophrenia is associated with a reduction of the lifespan by 20 years, with type II diabetes and cardiovascular disease contributing the most to the increased mortality. Unrecognised or silent myocardial infarction (MI) occurs in ~30% of the population, but the rates of unrecognised MI in patients with schizophrenia have only been sparsely investigated. METHOD: Electrocardiograms (ECG) from three psychiatric hospitals in Denmark were manually interpreted for signs of previous MI. Subsequently, ECGs were linked to the National Patient Registry in order to determine whether patients had a diagnosis consistent with previous MI. RESULTS: A total of 937 ECGs were interpreted, 538 men (57.4%) and 399 women (42.6%). Mean age at the time of ECG acquisition was 40.6 years (95% CI: 39.7-41.5, range: 15.9-94.6). We identified 32 patients with positive ECG signs of MIs. Only two of these patients had a diagnosis of MI in the National Patient Registry. An additional number of eight patients had a diagnosis of MI in the Danish National Patient Registry, but with no ECG signs of previous MI. This means that 30 out of 40 (75%) MIs were unrecognised. Only increasing age was associated with unrecognised MI in a stepwise multiple logistic regression model compared with patients with no history of MI, OR: 1.03 per year of age, 95% CI: 1.00-1.06, p=0.021. CONCLUSION: Unrecognised MI is common among patients with schizophrenia and may contribute to the increased mortality found in this patient group.