Derivation and Validation of Thresholds Using Synthetic Data Methods for Single-Test Screening of Emergency Department Patients with Possible Acute Myocardial Infarction Using a Point-of-Care Troponin Assay.

BACKGROUND: Single-sample (screening) rule-out of acute myocardial infarction (AMI) with troponin requires derivation of a single-test screening threshold. In data sets with small event numbers, the lowest one or two concentrations of myocardial infarction (MI) patients dictate the threshold. This is not optimal. We aimed to demonstrate a process incorporating both real and synthetic data for deriving such thresholds using a novel pre-production high-precision point-of-care assay. METHODS: cTnI concentrations were measured from thawed plasma using the Troponin I Next (TnI-Nx) assay (i-STAT; Abbott) in adults on arrival to the emergency department with symptoms suggestive of AMI. The primary outcome was an AMI or cardiac death within 30 days. We used internal-external validation with synthetic data production based on clinical and demographic data, plus the measured TnI-Nx concentration, to derive and validate decision thresholds for TnI-Nx. The target low-risk threshold was a sensitivity of 99% and a high-risk threshold specificity of >95%. RESULTS: In total, 1356 patients were included, of whom 191 (14.1%) had the primary outcome. A total of 500 synthetic data sets were constructed. The mean low-risk threshold was determined to be 5 ng/L. This categorized 38% (95% CI, 6%-68%) to low-risk with a sensitivity of 99.0% (95% CI, 98.6%-99.5%) and a negative predictive value of 99.4% (95% CI, 97.6%-99.8%). A similarly derived high-risk threshold of 25 ng/L had a specificity of 95.0% (95% CI, 94.8%-95.1%) and a positive predictive value of 74.8% (95% CI, 71.5%-78.0%). CONCLUSIONS: With the TnI-Nx assay, we successfully demonstrated an approach using synthetic data generation to derive low-risk thresholds for safe and effective screening.

Cost effectiveness of a 1-hour high-sensitivity troponin-T protocol: An analysis of the RAPID-TnT trial.

BACKGROUND: To understand the economic impact of an accelerated 0/1-hour high-sensitivity troponin-T (hs-cTnT) protocol. OBJECTIVE: To conduct a patient-level economic analysis of the RAPID-TnT randomised trial in patients presenting with suspected acute coronary syndrome (ACS). METHODS: An economic evaluation was conducted with 3265 patients randomised to either the 0/1-hour hs-cTnT protocol (n = 1634) or the conventional 0/3-hour standard-of-care protocol (n = 1631) with costs reported in Australian dollars. The primary clinical outcome was all-cause mortality or new/recurrent myocardial infarction. RESULTS: Over 12-months, mean per patient costs were numerically higher in the 0/1-hour arm compared to the conventional 0/3-hour arm (by $472.49/patient, 95% confidence interval [95 %CI]: $-1,380.15 to $2,325.13, P = 0.617) with no statistically significant difference in primary outcome (0/1-hour: 62/1634 [3.8%], 0/3-hour: 82/1631 [5.0%], HR: 1.32 [95 %CI: 0.95-1.83], P = 0.100). The mean emergency department (ED) length of stay (LOS) was significantly lower in the 0/1-hour arm (by 0.62 h/patient, 95 %CI: 0.85 to 0.39, P < 0.001), but the subsequent 12-month unplanned inpatient costs was numerically higher (by $891.22/patient, 95 %CI: $-96.07 to 1,878.50, P = 0.077). Restricting the analysis to patients with hs-cTnT concentrations ≤ 29 ng/L, mean per patient cost remained numerically higher in the 0/1-hour arm (by $152.44/patient, 95 %CI:$-1,793.11 to $2,097.99, P = 0.988), whilst the reduction in ED LOS was more pronounced (by 0.70 h/patient, 95 %CI: 0.45-0.95, P < 0.001). CONCLUSIONS: There were no differences in resource utilization between the 0/1-hour hs-cTnT protocol versus the conventional 0/3-hour protocol for the assessment of suspected ACS, despite improved initial ED efficiency. Further refinements in strategies to improve clinical outcomes and subsequent management efficiency are needed.

Implementation of more sensitive cardiac troponin T assay in a state-wide health service.

AIMS: Explore the impact of deploying high-sensitivity (hs) cardiac troponin T (cTnT) assay across a state-wide health service. METHODS AND RESULTS: Presentations to emergency departments of six tertiary hospitals between January 2008 and August 2019 were included; standard cTnT assay was superseded by hs-cTnT in June 2011 without changing the reference range (≥30 ng/L reported as elevated), despite cTnT level of 30 ng/L being equivalent to ∼44 ng/L with hs-cTnT. Clinical outcomes were captured using state-wide linked health records. Interrupted time series analyses were used adjusted for seasonality and multiple co-morbidities using propensity score matching allowing for correlation within hospitals. In total, 614,847 presentations had ≥1 troponin measurement. Clinical ordering of troponin decreased throughout the study with no increase in elevated measurements amongst those tested with hs-cTnT. Small but statistically significant changes in index myocardial infarction (MI) diagnosis (-0.36%/year, 95%CI [confidence interval]:-0.48, -0.24,p < 0.001) and invasive coronary angiography (0.12%/year,95%CI:0, 0.24,p = 0.02) were seen, with no impact on death/MI at 30 days or 3-year survival in episodes of care (EOCs) with elevated cTnT after hs-cTnT implementation. Length of stay (LOS) was shorter among those with an elevated hs-cTnT (-4.44 h/year, 95%CI:-5.27, -3.60, p < 0.001). Non-elevated cTnT EOCs demonstrated shorter total LOS and improved 3-year survival (adjusted hazard ratio:0.90, 95%CI:0.83, 0.97,p = 0.008) although death/MI at 30 days was unchanged using hs-cTnT. CONCLUSION: Widespread implementation of hs-cTnT without altering clinical thresholds reported to clinicians provided significantly shorter LOS without a clinically significant impact on clinical outcomes. A safer cohort with non-elevated cTnT was identified by hs-cTnT compared to the standard cTnT assay.

Classification performance of clinical risk scoring in suspected acute coronary syndrome beyond a rule-out troponin profile.

AIMS: High-sensitivity cardiac troponin strategies can provide risk stratification in patients with suspected acute coronary syndrome (ACS) in the emergency department (ED). This study evaluated whether clinical risk scoring improves the classification performance of a rule-out profile in suspected ACS. METHODS AND RESULTS: Patients presenting to ED with suspected ACS as part of the RAPID-TnT trial randomized to the intervention arm were included. Results ≥5 ng/L were available for all participants in this analysis. We evaluated the Thrombolysis In Myocardial Infarction (TIMI) risk score, History ECG Age Risk factors Troponin (HEART) score, and Emergency Department Assessment of Chest pain Score (EDACS) in addition to a rule-out profile based on the 0/1-h high-sensitivity cardiac troponin T protocol (<5 ng/L or ≤12 ng/L and a change of <3 ng/L at 1-h) using test performance parameters focusing on low-risk groups to identify the primary endpoint (TIMI ≤ 1, HEART ≤ 3, EDACS < 16). Primary endpoint was a composite of type 1/2 myocardial infarction (MI) at index presentation and all-cause mortality or type 1/2 MI at 30 days. A total of 3378 participants were enrolled between August 2015 and April 2019 of which 108 were ineligible/withdrew consent (intervention arm: n = 1638). Sensitivity, specificity, negative predictive value (NPV), and area under the curve (AUC) of the rule-out profile was 94.4%, 76.8%, 99.6%, and 0.86, respectively with 72.9% identified as 'low-risk'. Adding the clinical risk scores did not improve the sensitivity, NPV, or AUC with significantly lower specificity and 'low-risk' classified participants. CONCLUSIONS: Addition of clinical risk scores to rule-out profile did not demonstrate improved classification performance for identifying the composite of type 1/2 MI at index presentation and all-cause mortality or type 1/2 MI at 30 days. CLINICAL TRIALS REGISTRATION: URL: https://www.anzctr.org.au. Reg. No. ACTRN12615001379505.

Late Outcomes of the RAPID-TnT Randomized Controlled Trial: 0/1-Hour High-Sensitivity Troponin T Protocol in Suspected ACS.

BACKGROUND: High-sensitivity troponin assays are increasingly being adopted to expedite evaluation of patients with suspected acute coronary syndromes. Few direct comparisons have examined whether the enhanced performance of these assays at low concentrations leads to changes in care that improves longer-term outcomes. This study evaluated late outcomes of participants managed under an unmasked 0/1-hour high-sensitivity cardiac troponin T (hs-cTnT) protocol compared with a 0/3-hour masked hs-cTnT protocol. METHODS: We conducted a multicenter prospective patient-level randomized comparison of care informed by unmasked 0/1-hour hs-cTnT protocol (reported to <5 ng/L) versus standard practice masked hs-cTnT testing (reported to ≤29 ng/L) assessed at 0/3 hours and followed participants for 12 months. Participants included were those presenting to metropolitan emergency departments with suspected acute coronary syndromes, without ECG evidence of coronary ischemia. The primary end point was time to all-cause death or myocardial infarction using Cox proportional hazards models adjusted for clustering within hospitals. RESULTS: Between August 2015 and April 2019, we randomized 3378 participants, of whom 108 withdrew, resulting in 12-month follow-up for 3270 participants (masked: 1632; unmasked: 1638). Among these, 2993 (91.5%) had an initial troponin concentration of ≤29 ng/L. Deployment of the 0/1-hour hs-cTnT protocol was associated with reductions in functional testing. Over 12-month follow-up, there was no difference in invasive coronary angiography (0/1-hour unmasked: 232/1638 [14.2%]; 0/3-hour masked: 202/1632 [12.4%]; P=0.13), although an increase was seen among patients with hs-cTnT levels within the masked range (0/1-hour unmasked arm: 168/1507 [11.2%]; 0/3-hour masked arm: 124/1486 [8.3%]; P=0.010). By 12 months, all-cause death and myocardial infarction did not differ between study arms overall (0/1-hour: 82/1638 [5.0%] versus 0/3-hour: 62/1632 [3.8%]; hazard ratio, 1.32 [95% CI, 0.95-1.83]; P=0.10). Among participants with initial troponin T concentrations ≤29 ng/L, unmasked hs-cTnT reporting was associated with an increase in death or myocardial infarction (0/1-hour: 55/1507 [3.7%] versus 0/3-hour: 34/1486 [2.3%]; hazard ratio, 1.60 [95% CI, 1.05-2.46]; P=0.030). CONCLUSIONS: Unmasked hs-cTnT reporting deployed within a 0/1-hour protocol did not reduce ischemic events over 12-month follow-up. Changes in practice associated with the implementation of this protocol may be associated with an increase in death and myocardial infarction among those with newly identified troponin elevations. Registration: URL: https://www.anzctr.org.au; Unique identifier: ACTRN12615001379505.

A Randomized Trial of a 1-Hour Troponin T Protocol in Suspected Acute Coronary Syndromes: The Rapid Assessment of Possible Acute Coronary Syndrome in the Emergency Department With High-Sensitivity Troponin T Study (RAPID-TnT).

BACKGROUND: High-sensitivity troponin assays promise earlier discrimination of myocardial infarction. Yet, the benefits and harms of this improved discriminatory performance when incorporated within rapid testing protocols, with respect to subsequent testing and clinical events, has not been evaluated in an in-practice patient-level randomized study. This multicenter study evaluated the noninferiority of a 0/1-hour high-sensitivity cardiac troponin T (hs-cTnT) protocol in comparison with a 0/3-hour masked hs-cTnT protocol in patients with suspected acute coronary syndrome presenting to the emergency department (ED). METHODS: Patients were randomly assigned to either a 0/1-hour hs-cTnT protocol (reported to the limit of detection [<5 ng/L]) or masked hs-cTnT reported to ≤29 ng/L evaluated at 0/3-hours (standard arm). The 30-day primary end point was all-cause death and myocardial infarction. Noninferiority was defined as an absolute margin of 0.5% determined by Poisson regression. RESULTS: In total, 3378 participants with an emergency presentation were randomly assigned between August 2015 and April 2019. Ninety participants were deemed ineligible or withdrew consent. The remaining participants received care guided either by the 0/1-hour hs-cTnT protocol (n=1646) or the 0/3-hour standard masked hs-cTnT protocol (n=1642) and were followed for 30 days. Median age was 59 (49-70) years, and 47% were female. Participants in the 0/1-hour arm were more likely to be discharged from the ED (0/1-hour arm: 45.1% versus standard arm: 32.3%, P<0.001) and median ED length of stay was shorter (0/1-hour arm: 4.6 [interquartile range, 3.4-6.4] hours versus standard arm: 5.6 (interquartile range, 4.0-7.1) hours, P<0.001). Those randomly assigned to the 0/1-hour protocol were less likely to undergo functional cardiac testing (0/1-hour arm: 7.5% versus standard arm: 11.0%, P<0.001). The 0/1-hour hs-cTnT protocol was not inferior to standard care (0/1-hour arm: 17/1646 [1.0%] versus 16/1642 [1.0%]; incidence rate ratio, 1.06 [ 0.53-2.11], noninferiority P value=0.006, superiority P value=0.867), although an increase in myocardial injury was observed. Among patients discharged from ED, the 0/1-hour protocol had a negative predictive value of 99.6% (95% CI, 99.0-99.9%) for 30-day death or myocardial infarction. CONCLUSIONS: This in-practice evaluation of a 0/1-hour hs-cTnT protocol embedded in ED care enabled more rapid discharge of patients with suspected acute coronary syndrome. Improving short-term outcomes among patients with newly recognized troponin T elevation will require an evolution in management strategies for these patients. CLINICAL TRIAL REGISTRATION: URL: https://www.anzctr.org.au. Unique identifier: ACTRN12615001379505.

Application of High-Sensitivity Troponin in Suspected Myocardial Infarction.

BACKGROUND: Data regarding high-sensitivity troponin concentrations in patients presenting to the emergency department with symptoms suggestive of myocardial infarction may be useful in determining the probability of myocardial infarction and subsequent 30-day outcomes. METHODS: In 15 international cohorts of patients presenting to the emergency department with symptoms suggestive of myocardial infarction, we determined the concentrations of high-sensitivity troponin I or high-sensitivity troponin T at presentation and after early or late serial sampling. The diagnostic and prognostic performance of multiple high-sensitivity troponin cutoff combinations was assessed with the use of a derivation-validation design. A risk-assessment tool that was based on these data was developed to estimate the risk of index myocardial infarction and of subsequent myocardial infarction or death at 30 days. RESULTS: Among 22,651 patients (9604 in the derivation data set and 13,047 in the validation data set), the prevalence of myocardial infarction was 15.3%. Lower high-sensitivity troponin concentrations at presentation and smaller absolute changes during serial sampling were associated with a lower likelihood of myocardial infarction and a lower short-term risk of cardiovascular events. For example, high-sensitivity troponin I concentrations of less than 6 ng per liter and an absolute change of less than 4 ng per liter after 45 to 120 minutes (early serial sampling) resulted in a negative predictive value of 99.5% for myocardial infarction, with an associated 30-day risk of subsequent myocardial infarction or death of 0.2%; a total of 56.5% of the patients would be classified as being at low risk. These findings were confirmed in an external validation data set. CONCLUSIONS: A risk-assessment tool, which we developed to integrate the high-sensitivity troponin I or troponin T concentration at emergency department presentation, its dynamic change during serial sampling, and the time between the obtaining of samples, was used to estimate the probability of myocardial infarction on emergency department presentation and 30-day outcomes. (Funded by the German Center for Cardiovascular Research [DZHK]; ClinicalTrials.gov numbers, NCT00470587, NCT02355457, NCT01852123, NCT01994577, and NCT03227159; and Australian New Zealand Clinical Trials Registry numbers, ACTRN12611001069943, ACTRN12610000766011, ACTRN12613000745741, and ACTRN12611000206921.).

Validity of a Novel Point-of-Care Troponin Assay for Single-Test Rule-Out of Acute Myocardial Infarction.

Importance: Emergency department (ED) investigations of patients with suspected acute myocardial infarction (AMI) are time consuming, partly because of the turnaround time of laboratory tests. Current point-of-care troponin assays shorten test turnaround times but lack precision at lower concentrations. Development of point-of-care troponin assays with greater analytical precision could reduce the decision-making time in EDs for ruling out AMI. Objective: To determine the clinical accuracy for AMI of a single troponin concentration measured on arrival to ED with a new-generation, higher precision point-of-care assay with a 15-minute turnaround time. Design, Setting, and Participants: This observational study occurred at a single urban regional ED. Adults presenting acutely from the community to the ED with symptoms suggestive of AMI were included. Troponin concentrations were measured on ED arrival with both a novel point-of-care assay (i-STAT TnI-Nx; Abbott Point of Care) and a high-sensitivity troponin I assay (Architect hs-cTnI; Abbott Diagnostics). Main Outcomes and Measures: The primary outcome was type 1 AMI during index presentation. We compared the discrimination ability of the TnI-Nx assay with the hs-cTnI assay using the area under receiver operator characteristic curve (AUC) and sensitivity, negative predictive value, and the proportion of negative test results at thresholds with 100% sensitivity. Results: Of 354 patients (255 [72.0%] men; mean [SD] age, 62 [12] years), 57 (16.1%) experienced an AMI. Eighty-five patients (24.0%) presented to the ED less than 3 hours after symptom onset. No difference was found between the AUC of the TnI-Nx assay (0.975 [95% CI, 0.958-0.993]) and the hs-cTnI assay (0.970 [95% CI, 0.949 to 0.990]; P = .46). A TnI-Nx assay result of less than 11 ng/L identified 201 patients (56.7%) as low risk, with a sensitivity of 100% (95% CI, 93.7%-100%) and a negative predictive value of 100% (95% CI, 98.2%-100%). In comparison, an hs-cTnI assay result of less than 3 ng/L identified 154 patients (43.5%) as low risk, with a sensitivity of 100% (95% CI, 93.7%-100%) and a negative predictive value of 100% (95% CI, 97.6%-100%). Conclusions and Relevance: A novel point-of-care troponin assay that can produce a result 15 minutes after blood sampling had comparable discrimination ability to an hs-cTnI assay for ruling out AMI after a single blood test. Use in the ED may facilitate earlier decision making and could expedite the safe discharge of a large proportion of low-risk patients.

Early Rule-Out and Rule-In Strategies for Myocardial Infarction.

BACKGROUND: Patients with chest pain comprise a large proportion of emergency presentations and place a major burden on healthcare resources. Therefore, efforts to safely and rapidly identify those with and without acute myocardial infarction (AMI) are needed. The challenge for clinicians is to accurately identify patients with acute coronary syndromes, while balancing the need to safely and rapidly reassure and discharge those without serious conditions. CONTENT: This review summarizes the evidence to date on optimum accelerated strategies for the rule-in and rule-out of AMI, using strategies focused on optimum use of troponin results. Evidence based on both sensitive and highly sensitive troponin assay results is presented. The use of novel biomarkers is also addressed and the combination of biomarkers with other clinical information in accelerated diagnostic strategies is discussed. SUMMARY: The majority of patients, who are not at risk of myocardial infarction or other serious harm, may be suitable for discharge directly from the emergency setting using approaches focused on troponin algorithms and accelerated diagnostic protocols. Evidence about the clinical and health economic impact of use of such strategies is needed, as they may have major benefits for both patients and healthcare providers.