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Novel protocol with high-sensitivity troponin T accurately rules out MI
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A novel high-sensitivity troponin T protocol accurately ruled out MI in patients who visited an ED, according to a research letter published in Circulation.
“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,” Rebecca Vigen, MD, MSCS, cardiologist at UT Southwestern Medical Center in Dallas, said in a press release.
Researchers assessed the accuracy of the novel protocol in 536 patients (mean age, 55 years; 44% women) who presented with MI symptoms without ST elevations on ECG at an ED between August and October 2017.
The novel protocol, which included a 3-hour high-sensitivity troponin T measurement (Elecsys Troponin T Gen 5 STAT, Roche Diagnostics), was compared with a conventional fourth-generation high-sensitivity troponin T assay, which was tested at baseline and more than 3 hours after the patient presented with symptoms. Troponin T and high-sensitivity troponin T were measured at 0, 1 and 3 hours after presentation at the ED.
Patients were then categorized based on their high-sensitivity troponin T levels and changes. A patient was ruled out for MI if troponin T levels were less than 0.01 ng/mL for all measurements, whereas those considered to be abnormal had values greater than 0.01 ng/mL.
MI was diagnosed in 2.1% of patients, nonischemic myocardial injury was diagnosed in 17% and unstable angina was diagnosed in 0.4%.
The new high-sensitivity troponin T protocol ruled out MI in 83.8% of patients by 3 hours vs. 80.4% of patients using the conventional assay. With the new protocol, 30% of patients were ruled out at baseline, 24.8% at 1 hour and 28.9% at 3 hours.
The conventional assay determined that 19.6% of patients were abnormal vs. 16.2% using the new protocol (P = .03).
The sensitivity and negative predictive value of the new protocol was 100%, the positive predictive value was 13% and the specificity was 86%.
During 30 days of follow-up, no recurrent MI events occurred in the patients who were ruled out.
“Clinical judgment remains essential in the interpretation of abnormal troponin values as the [high-sensitivity troponin T] assay becomes adopted in the United States, where troponin is measured more indiscriminately than in many other countries,” Vigen and colleagues wrote. – by Darlene Dobkowski
Disclosures: Vigen reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.
Perspective
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Joseph S. Alpert, MD
Last month in the Journal of the American College of Cardiology, we wrote an editorial (Alpert JS, et al. J Am Coll Cardiol. 2018;doi:10.1016/j.jacc.2018.05.041) pointing out just what the researchers are reporting here, that is in the American setting, when you see patients who do not present with typical chest pain, you need more than 1 hour.
The 1-hour protocol works if you are looking at typical patients who present with chest pain, but as it turns out, when we looked at the numbers, the mean age of the individuals they are looking at is much younger than the individuals in the U.S. that we consider for MI or ACS. The reason for that is that many people present atypically. Sometimes they present with shortness of breath and no chest pain. Sometimes older patients present with confusion and no chest pain. If you include all those people, a recent report from UT Southwestern Medical Center points out that you need 3 hours.
The first high-sensitivity troponin test was approved by the FDA last year and is being rolled out. There are a number of places doing research on it, like UT Southwestern, Mayo Clinic in Rochester and Brigham and Women’s Hospital. We are talking about a tiny fraction of American hospitals.
The other hospitals are getting in line, my hospital included. In about 8 months, we will have the high-sensitivity test. We are part of a big system called Banner, that totals about two-thirds of the beds in Arizona. As the contracts for the old troponin test run out, they are bringing in the new test.
We need data from non-university hospitals. We need big community research about what percentage is picked up at 1 hour, 2 hours and 3 hours. My expectation is that most American emergency rooms will follow a 3-hour protocol. If there is any question, keep the patient a little longer.
No. 1, the high-sensitivity troponin is a positive. It allows us to send a lot of patients out of the emergency room sooner than before. No. 2, it is more sensitive and more specific, but of course it is going to pick up people who have had non-ischemic myocardial injuries. That is the reason why its specificity is not so great. We saw that in the Circulation article. It is because you can have elevations in troponin from other things. For example, myocarditis, viral infection in the heart, trauma, cerebral injuries. Also, patients who are very sick with sepsis and so forth can have elevated troponin from a non-ischemic myocardial injury or also so-called type 2 MIs secondary to hypotension or severe tachycardia.
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