Researchers were able to rule out myocardial infarction in 30% of patients immediately, and another 25% of patients at 1 hour. By 3 hours, the assay had successfully ruled out MI in 83.8% of patients, versus the 80.4% ruled out under the conventional assay.
Rebecca Vigen, MD
A new test that can distinguish the early events of a heart attack in patients arriving in emergency rooms (ERs) has been proven safe and effective.
Analysis of the recently US Food and Drug Administration (FDA)-approved high-sensitivity (hs) troponin T (cTnT) assay has returned results which indicate the test designed to rule out myocardial infarction (MI) in low-risk patients at the ER is both safe and effective.
The novel hs-cTnT assay, developed by a team from the Parkland Health and Hospital System in Dallas, TX, improved on the sensitivity and precision of the conventional fourth-generation cTnT assay predominately used in the US. Its precision was previously indicated by overseas analysis;the European Society of Cardiology (ESC) guidelines endorsed a 0/1-hour rule-out speed using the assay.
In the new test, researchers assessed the assay in 536 patients admitted to an ER with MI symptoms including chest pains and shortness of breath. Mean patient age was 55 years, and the population was 44% women.
Both cTnT and hs-cTnT were measured at baseline, 1, and 3 hours after patient presentation at Parkland Health and Hospital System ER. Patients were classified into either “ruled out” or “abnormal” categories, based on hs-cTnT levels and change values. Patients ruled out had reported cTnT at <0.01 ng/mL with the conventional assay at all time points, while patients classified as abnormal had cTnT ≥0.01 ng/mL.
A final diagnosis was provided by 3 cardiologists, based on the provided clinical information which included the cTnT assay results. The sensitivity of the hs-cTnT assay was assessed in a second adjudication without the cTnT assay results.
Researchers were able to rule out MI in 30% of patients immediately, and another 25% of patients at 1 hour. By 3 hours (28.9%), the assay had successfully ruled out MI in 83.8% of patients, versus the 80.4% ruled out under the conventional assay. Just 16.2% of patients were abnormal under the new assay, versus 19.6% on the conventional (P= 0.03).
The novel assay also did not miss a single MI in the patient population, lead author Rebecca Vigen, MD, a cardiologist at the University of Texas Southwestern Medical Center, said.
"The test also allowed us to determine faster that many patients who had symptoms of a heart attack were not having a heart attack than if we had relied on the traditional test,” Vigen said.
The hs-cTnT protocal reported sensitivity and negative predictive values of 100%, specificity of 86%, and positive predictive value of 13% in the observed patients.
With outstanding results indicating its efficacy in a real-world setting, Vigen expressed hope other institutions may follow suit in considering the novel assay.
“We anticipate that this procedure will allow many patients with chest pain to be given a 'yes' or 'no' diagnosis of whether they are having a heart attack faster,” Vigen said.
The study, "Evaluation of a Novel Rule-Out Myocardial Infarction Protocol Incorporating High-Sensitivity Troponin T in a US Hospital," was published online in the American Heart Association's Cardiology journal on Monday.