Is it possible to exclude a diagnosis of myocardial damage within six hours of admission to an emergency department? Diagnostic cohort study

Objective To assess the clinical efficacy and accuracy of an emergency depa rtment based six hour rule-out protocol for myocardial damage. Design Diagnostic cohort study. Setting Emergency department of an inner ci ty university hospital. Participants 383 consecutive patients aged over 25 years with chest pain of less than 12 hours' duration who were at low to moderate risk of acute myo cardial infarction. Intervention Serial measurements of creatine kinase MB mass and continuous ST segment monitoring for six hours with 12 leads. Main outcome measure Performance of the diagnostic test against a gold stan dard consisting of either a 48 hour measurement of troponin T concentration or screening for myocardial infarction according to the World Health Organ ization's criteria. Results Outcome of the gold standard test was available for 292 patients. O n the diagnostic test for the protocol, 53 patients had positive results an d 239 patients had negative results. There were 18 false positive results a nd one false negative result. Sensitivity was 97.2% (95% confidence interva l 95.0% to 99.0%), specificity 93.0% (90.0% to 96.0%), the negative predict ive value 99.6%, and the positive predictive value 66.0%. The positive like lihood ratio was 13.9 and the negative likelihood ratio 0.03. Conclusions The six hour rule-out protocol for myocardial infarction is acc urate mad efficacious. It can be used in patients presenting to emergency d epartments with chest pain indicating a low to moderate risk of myocardial infarction.