Troponin Limit of Detection Plus Cardiac Risk Stratification Scores to Rule Out Acute Myocardial Infarction and
Mitchell D Datlow1, Kelly M Gray, Adriel Watts
1*Department of Emergency Medicine, University of California Davis School of Medicine, Sacramento, CA; and †Department of Emergency Medicine, UT Southwestern Medical Center.
Insights
A low-risk HEART score or low ACS Pretest Probability combined with a troponin below the limit of detection can effectively rule out acute myocardial infarction (AMI) and 30-day major adverse cardiac events (MACE). This approach enhances diagnostic accuracy for cardiac events.
Area of Science:
- Cardiology
- Emergency Medicine
- Diagnostic Accuracy
Background:
- Troponin levels below the 99th percentile are considered normal for acute myocardial infarction (AMI) screening.
- The limit of detection (LOD) for troponin assays presents challenges in definitively ruling out cardiac events.
Purpose of the Study:
- To test the hypothesis that a low-risk HEART score (0-3) or low ACS Pretest Probability (<2%) plus a single troponin below the LOD can rule out AMI and 30-day major adverse cardiac events (MACE).
- To evaluate the sensitivity of these combined strategies for ruling out AMI and MACE.
Main Methods:
- Retrospective study of 888 patients presenting to an academic emergency department who received troponin I testing.
- Data abstraction from electronic medical records for demographic and clinical information.
- Primary outcome: final diagnosis of myocardial infarction. Secondary outcome: 30-day MACE (myocardial infarction, revascularization, or cardiac/uncertain death).
Main Results:
- Low-risk HEART score and low ACS Pretest Probability alone showed high sensitivity for AMI (98% and 96%) and 30-day MACE (94% and 95%).
- Combining either score with a troponin below the LOD achieved 100% sensitivity for both AMI and 30-day MACE.
- The addition of troponin below LOD significantly improved sensitivity for 30-day MACE in both low-risk groups.
Conclusions:
- A low-risk HEART score or low ACS Pretest Probability, when accompanied by a single troponin below the LOD, can reliably rule out AMI.
- This combined approach demonstrates 100% sensitivity for ruling out 30-day MACE, offering a safe and effective strategy for risk stratification.
- The study supports the use of these combined criteria to expedite the evaluation of emergency department patients with suspected cardiac events.
Abstract:
When screening for acute myocardial infarction (AMI), troponin levels below the 99th percentile, including those below the limit of detection (LOD), are considered normal. We hypothesized that a low-risk HEART score (0-3) or ACS Pretest Probability Assessment <2% plus a single troponin below the LOD would rule out both AMI and 30-day major adverse cardiac events (MACE). We studied all patients who presented to a single academic emergency department and received a troponin I (Siemens Ultra Troponin I) from September 1, 2013, to November 13, 2013 (n=888). Demographic and clinical data were abstracted from the electronic medical record. Primary outcome was a final encounter diagnosis of myocardial infarction. Secondary outcome was 30-day MACE, defined as composite of myocardial infarction, revascularization, or death from a cardiac or uncertain etiology. Sensitivities of low-risk HEART score and ACS Pretest Probability <2% alone were 98% (95% confidence interval [CI], 89%-100%) and 96% (95% CI, 86%-100%) for AMI and 94% (95% CI, 86%-98%) and 95% (95% CI, 88%-99%), respectively, for 30-day MACE. When combined with troponin below the LOD, sensitivity for AMI was 100% (95% CI, 93%-100%; difference 2%; 95% CI, -2% to 6%) for low-risk HEART Score and 100% (95% CI, 93%-100%; difference 4%; 95% CI, -1.5% to 10%) for ACS Pretest Probability <2%. When combined with troponin below the LOD, sensitivity for 30-day MACE was 100% (95% CI, 95%-100%; difference 6%; 95% CI, 1%-12%) for low-risk HEART Score and 100% (95% CI, 95%-100%; difference 5%; 95% CI, 0.2%-10%) for ACS Pretest Probability <2%. Addition of a single troponin below the LOD to these scores improves sensitivity for 30-day MACE.
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