One-hour rule-out and rule-in of acute myocardial infarction using Siemens high-sensitivity cardiac troponin T

Background: High-sensitivity cardiac troponin (hs-cTn) assays seem to improve the early diagnosis of acute myocardial infarction (AMI), but it is unknown how to best use them in clinical practice. Our objective was to develop an algorithm for rapid rule-out and rule-in of AMI. Methods: A prospective multicenter study enrolling 946 unselected patients with acute chest pain presenting to the ED. Siemens high-sensitivity cardiac troponin I (hs-cTnI) was measured in a blinded fashion at presentation and after 1 hour. The final diagnosis was adjudicated by 2 independent cardiologists. A hs-cTnI algorithm incorporating baseline values as well as absolute changes within the first hour was derived from all patients. The primary prognostic end point was death during 30 days of follow-up. Results: AMI was the final diagnosis in 18% of patients. According to our rule-in and rule-out algorithm (figure 1), 469 patients (50%) could be classified as "rule-out", 172 patients (18%) as "rule-in", and 305 patients (32%) as in the "observational zone" within 1 hour. Overall, this resulted in a sensitivity and negative predictive value of 97% and 99% for rule-out, a specificity and positive predictive value of 95% and 76%, respectively, for rule-in, and a prevalence of AMI of 10% in the observational zone group. Cumulative 30-day survival was 99.6%, 99.0%, and 95.3% (P<.001) in patients classified as ruleout, observational zone, and rule-in, respectively. Conclusions: Using a simple algorithm incorporating hs-cTnI baseline values and absolute changes within the first hour allowed a safe rule-out as well as an accurate rule-in of AMI within 1 hour in 68% of unselected patients with acute chest pain. This novel strategy may obviate the need for prolonged monitoring and serial blood sampling in 2 of 3 patients.