One-Hour Rule-Out and Rule-In of Acute Myocardial Infarction Using High-Sensitivity Cardiac Troponin T
What is the performance of an algorithm that uses high-sensitivity cardiac troponin T (hs-cTnT) at presentation and after 1 hour among patients with acute chest pain?
This was a prospective multicenter study to develop and validate an algorithm to rule-in and rule-out acute myocardial infarction (AMI) using baseline levels and absolute changes within 1 hour of hs-cTnT in 872 randomly selected patients presenting to the emergency department with acute chest pain. The algorithm was developed among 436 patients in this sample and then validated among the other half. Adjudication of final diagnoses was performed by two independent cardiologists for all patients according to level of hs-cTnT. Rule-out criteria were defined to allow for a 100% sensitivity and negative predictive value. Rule-in criteria were defined by classification and regression tree (CART) analysis. Patients not fulfilling criteria for either rule-in or rule-out were assigned to “observational zone” status. The primary outcome was 30-day all-cause mortality.
AMI was the final diagnosis in 17% of patients. Application of the algorithm to the validation cohort within 1 hour of presentation allowed for classification of 259 patients (60%) as “rule-out,” 76 patients (17%) as “rule-in,” and 101 patients (23%) as “observational zone” status. This resulted in sensitivity and negative predictive value of 100% for rule-out; specificity and positive predictive value were 97% and 84%, respectively, among the rule-in group. The algorithm provided a definite diagnosis after 1 hour in 77% of patients. Thirty-day mortality was 0.2% in the rule-out group.
An algorithm based on hs-cTnT baseline values and absolute changes within 1 hour allowed for a safe rule-out or accurate rule-in among 77% of unselected patients with chest pain.
This study suggests that three out of four patients can be accurately classified within 1 hour of presentation using an hs-cTnT assay. Provided the algorithm can be confirmed and externally validated, the implications for such results are broad, and may obviate the need for prolonged monitoring and serial blood sampling in the majority of patients presenting with chest pain.
Prashant Vaishnava, MD
Keywords: Myocardial Infarction, Biological Markers, Troponin T
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