Evaluation of a 0-hour/1-hour algorithm in the diagnosis of myocardial infarction with high-sensitivity cardiac troponin T1.

of evidence The High Sensitivity Cardiac Troponin T Assay for Rapid Rule-out of Acute Myocardial Infarction trial was a prospective, multicentre, diagnostic study done at 12 sites, across three continents to validate the diagnostic accuracy of the troponin T 0-hour/1-hour algorithm for rule-in and rule-out of acute myocardial infarction. Current troponin assays for the diagnosis of myocardial infarction usually require serial sampling between 8 and 24 hours, depending on the specific assay/local protocols. This time interval contributes to ‘rule-in’ delays, delaying treatment, and ‘rule-out’ delays, costing time, money and resources. Stratifying patients with symptoms suggestive of acute myocardial infarction into three groups, by measuring the concentrations of cardiac troponin T at the time of presentation and after 1 hour, using a highly sensitive assay, could therefore speed up diagnosis and treatment, rule out disease more efficiently and save costs. The algorithm used was: ► ‘rule-in’ (0 hour≥52 ng/L or Δ1h≥5 ng/L). ► ‘rule out’ (0 hour<12 ng/L and Δ1h<3 ng/L). ► ‘observational zone’ (0 hour 12–52 ng/L and Δ1h 3–5 ng/L). The authors recruited patients presenting to the emergency department with symptoms suggestive of myocardial infarction (chest pain/angina), with onset of pain or maximum discomfort of pain within the previous 6 hours. Written informed consent was obtained and blood samples taken at 0 hour, 1 hour, 2 hours and 4 to 14 hours. Patients underwent standard clinical assessment and treatment (table 1). For the 1282 patients in the analysis, performance measures for the troponin T assay can be found in table 2. Two independent cardiologists adjudicated the diagnoses using all the available evidence. They were able to access standard troponin I results, but remained blinded to troponin T concentration. Secondary outcome measures included mortality at 30 days and 1 year. In the ‘observational’ group, 22.5% had acute myocardial infarction. Cumulative 30-day mortality was 0.1%, 0.7% and 2.7% in patients classified as rule-out, observational zone and rule-in respectively.