High Sensitivity Troponin T and Acute Myocardial Infarction: One and Done?

There has been a lot of publicity about evaluation of chest pain patients in the emergency department (ED) with high sensitivity troponin testing. In the past with older troponin assays, clinicians would evaluate patients, get an ECG, and an initial set of cardiac biomarkers. The subsequent set of biomarkers would be performed at 6-8 hours later before determination of disposition. In the past few years, several studies have been published evaluating point of care troponins,  sensitive troponins, and high sensitivity troponins which have changed our practice and evaluation of these patients.  An early version of a study was recently released in the Journal of the American College of Cardiology (JACC) stating that for ED chest pain patients, we may be able to discharge patients from the ED with an initial normal ECG and single high sensitivity troponin T (hs-cTnT). So is it true… one and done?

Google Hangout on Air with Dr. Holzmann

Citation: High Sensitivity Troponin T study¹

What they did:

• Retrospective study of 14,636 patients age ≥ 25 years presenting to an ED with chest pain, with at least one hs-cTnT and ECG over two year period in Stockholm, Sweden
• Compared patients with hs-cTnT of < 5 ng/L, 5 to 14 ng/L, and > 14 ng/L

Primary and Secondary Outcomes:

• Primary Outcomes: Fatal or non-fatal type 1 MI within 30 days of ED visit
• Secondary Outcomes: MI within 180 days and 365 days after the ED visit
• Also calculated hazard ratio for all-cause mortality in patients with first hs-cTnT of < 5 ng/L for admitted versus directly discharged from ED patients

Results:

• Mean age of 55 years old
• 61% (8,883 patients) of patients had initial hs-cTnT < 5 ng/L
  • 39 had diagnosis of MI and 2 died at 30 days
    • 15  of these 39 had no ECG changes
• 21% of patients had initial hs-cTnT between 5 – 14 ng/L
• 18% of patients had initial hs-cTnT > 14 ng/L
• Hospitalization rate of 21% in patients with initial hs-cTnT < 5 ng/L
  • 90% of these patients had a second hs-cTnT < 5 ng/L
  • 10% of these patients had a second hs-cTnT of between 5 – 14 ng/L or > 14 ng/L
  • 14% of patients were discharged home with diagnosis of MI
• If initial hs-cTnT < 5 ng/L AND ECG with no signs of ischemia:
  • NPV for MI and death at 30 days 99.8% and 100%, respectively
  • Absolute risk for MI 0.17%
  • No significant difference in the risk of death within 365 days between patients discharged directly form the ED vs admitted to hospital (HR 0.73 with CI 0.48 – 1.12)

Limitations:

• Retrospective study
• No external validation study

Author’s Conclusion: Patients with chief complaint of chest pain presenting to the ED with an initial hs-cTnT of < 5 ng/L and no signs of ischemia on ECG have minimal risk of MI and/or death at 3o days and can be safely discharged from the ED.

My Thoughts: Sensitivity vs Specificity

15 of 8,883 (0.2%) patients had a diagnosis of MI with initial hs-cTnT of < 5 ng/dL. But on the flip side only 676 of 2,579 (26%) patients with a hs-cTnT > 14 ng/dL had a diagnosis of MI at 30 days. Another way of stating this is the significance of a positive test is significantly reduced with higher sensitivity troponins (i.e. for what we gain in sensitivity we are giving up in specificity).

From a practical standpoint, would you then admit all your patients with indeterminant hs-cTnT’s (i.e. ≥ 5 ng/dL), knowing that the majority of these patients don’t have an AMI? The Associated Press recently published:

Dr. Allan Jaffe, a cardiologist at the Mayo Clinic, said the problem is not what the test rules out, but what it might falsely rule in. It’s so sensitive that it can pick up troponin from heart failure and other problems and cause unnecessary tests for that.

I look forward to seeing additional followup studies looking at hs-cTnT utility and generalizability. 

For more thoughts, also check out:

• Dr. Ryan Radecki from Emergency Medicine Literature of Note
• Ken Milne’s podcast at The Skeptics Guide to Emergency Medicine

Author information

Salim Rezaie, MD

ALiEM Associate Editor
Clinical Assistant Professor of EM and IM
University of Texas Health Science Center at San Antonio
Founder, Editor, Author of R.E.B.E.L. EM and REBEL Reviews

| Twitter | Google+ |

The post High Sensitivity Troponin T and Acute Myocardial Infarction: One and Done? appeared first on ALiEM.