1. .
Troponin limit of detection plus cardiac risk stratification scores for the exclusion of myocardial infarction and 30-day adverse cardiac events in ED patients
Kelly M. Gray, MD; Mitchell D. Datlow, MA; Deborah B. Diercks, MD, MSc; Bryn E. Mumma, MD, MAS
University of California Davis, Department of Emergency Medicine, Sacramento, CA
INTRODUCTION
FIGURE AND TABLES
RESULTS
888 patients
Median age 62 (IQR 52-74) years; 460 (52%) male (Table 2)
422 (48%) had initial troponin below the LOD
49 (5.5%) had encounter diagnosis of AMI
80 (11%) had 30-day composite outcome
HEART score sensitivity for AMI (Table 3)
Alone: 98% (95% CI 89–100%)
With troponin below the LOD: 100% (95% CI 93–100%; difference 2%, 95% CI -2–6%)
ACS Pretest Probability <2% sensitivity for AMI (Table 3)
Alone: 96% (95% CI 86–100%)
With troponin below the LOD: 100% (95% CI 93–100%; difference 4%, 95% CI -1.5–10%)
Over 10 million patients present to EDs in the US annually with chest pain; 10% have acute coronary syndromes
Evaluation for acute myocardial infarction (AMI) typically involves serial troponins
When screening for MI, troponins below the 99th percentile (0.04ng/ml), including those below the limit of detection (LOD; 0.01ng/ml), are considered normal
HEART Score and ACS Pretest Probability assessment can risk-stratify ED patients with possible AMI
Hypothesis: Low-risk HEART Score (0-3) or an ACS Pretest Probability Assessment < 2% plus an initial troponin below the LOD would exclude both AMI during admission and 30-day major adverse cardiac events
Table 1a. HEART Score
Table 2. Patient Characteristics
Variable
Score
History
Highly suspicious 2
Moderately suspicious 1
Slightly suspicious
EKG
Significant ST-depression
Non-specific repolarization disturbance
Normal
Age
≥ 65
45-64
< 45
Risk Factors
≥ 3 or history of atherosclerotic disease
1-2 risk factors
No known risk factors
Troponin
> 3 times the normal limit
1-3 times the normal limit
≤ normal limit
Total Score
Characteristics
N (%)
Demographic characteristics
Age (median)
62 (IQR 52-74)
Male sex
460 (52%)
Race/ethnicity
White, non-Hispanic
265 (30%)
White, Hispanic
72 (8%)
Black
115 (13%)
Asian
54 (6%)
Other
56 (6%)
Unreported
266 (30%)
Clinical characteristics
Chief complaint of chest pain
309 (35%)
Coronary artery disease
243 (27%)
Diabetes
329 (37%)
Smoking
246 (28%)
Troponin below LOD
422 (48%)
Risk Categories
Low Risk HEART score (0-3)
333 (38%)
ACS Pre-test Probability <2%
143 (16%)
30-day follow-up not available
151 (17%)
LIMITATIONS
METHODS
Table 1b. ACS Pretest Probability Assessment
Single center study
Relatively small sample size with low proportion of AMIs
30-day follow-up not available for 151 patients (17%)
Retrospective cohort study at single academic ED
Included patients who had a troponin I test (Siemens Ultra Troponin I) from 9/1/13 to 11/13/13
Excluded those with missing encounter diagnosis (n=21)
Abstracted data from electronic medical record:
Demographic and clinical characteristics
Laboratory and ECG results
Diagnoses
30-day return visits
Calculated HEART Score (Table 1a) & ACS Pretest Probability (Table 1b)
An ACS Pretest Probability cutpoint of <2% was chosen because HEART score 0-3 corresponds to <2% risk
Primary outcome = Final encounter diagnosis of AMI
Secondary outcome = Composite of MI, revascularization, and death from a cardiac or uncertain etiology at 30 days
Descriptive statistics presented
Table 3. Comparison of Sensitivities
Acute MI
(n=888)
Difference
30-day Composite
(n=737)
HEART Score 0-3
98%
(95%CI %) --
94%
(95%CI 86-98%)
ACS Pretest Probability <2%
96%
(95%CI %)
95%
(95%CI 88-99%)
Troponin below LOD
97%
(95%CI %)
89%
(95%CI 80-95%)
HEART Score Troponin below LOD
100%
(95%CI %) 2%
(95%CI -2 to 6%)
(95%CI %) 6%
(95%CI 1-12%)
ACS Pretest Probability <2% + Troponin below LOD 4%
(95% CI -1.5 to 10%) 5%
(95%CI %)
Variables
Age
Gender
Race
Chest pain w/ palpation
Personal history of CAD
Diaphoresis
EKG ST depression > 0.5mm
T Wave inversion > 0.5mm
CONCLUSIONS
Patients with an initial troponin I value below the LOD and a low-risk HEART Score or ACS Pretest Probability <2% had no acute MIs or 30-day adverse cardiac events
Addition of a single troponin below the LOD to these scores improves sensitivity for 30-day adverse cardiac events
ACKNOWLEDGEMENTS
This project was supported by the National Institutes of Health (NIH) through grants K12HL108964, K08HL130546, and UL1TR001860