Trial design for assessing analytical and clinical performance of high-sensitivity cardiac troponin I assays in the United States: The HIGH-US study

Design and Analytical Evaluation of Novel Cardiac Troponin Assays Targeting Multiple Forms of the Cardiac Troponin I-Cardiac Troponin T-Troponin C Complex and Fragmentation Forms

BACKGROUND

Current studies suggest that cardiac troponin (cTn) forms in the circulation may vary in different clinical scenarios. Our aim was to design a combination of cTn assays specific to the main cTn forms and to evaluate their analytical performance.

METHODS

We developed immunoassays specific for measuring (1) long-cTnT cTnI-cTnT-TnC (ITC) ternary complex, with cTnT in long form without cleavage at the C-terminal amino acids residue 189-223, designated "long-cTnT ITC complex assay;" (2) both the long-cTnT ITC complex plus short-cTnT ITC complex, designated "hs-total ITC complex assay;" (3) the central part of cTnT of both the long-cTnT ITC complex and free cTnT, designated "hs-cTnT assay." Sex-specific 99th percentile upper reference limits (URLs) were determined. High-sensitivity performance was assessed by examining the imprecision and detectable results above limit of detection (LoD) in the healthy population.

RESULTS

Both complex immunoassays exhibited excellent analytical sensitivity, precision, and specificity. The 99th percentile URLs were as follows: long-cTnT ITC complex: male 0.90 ng/L, female 0.87 ng/L; hs-total ITC complex: male 16.15 ng/L, female 10.08 ng/L; hs-cTnT: male 15.57 ng/L, female 14.28 ng/L. The total imprecision at or below the sex-specific 99th percentile URLs was <5% for all assays. The hs-total ITC complex and the hs-cTnT assays showed >50% of measurable concentrations above the LoD. However, <20% were measurable for the long-cTnT ITC complex assay.

CONCLUSIONS

The cTn assays detected concentrations of major cTn forms in the circulation with high sensitivity, precision, and specificity, supporting their use for monitoring cTn complex and fragmentation forms during myocardial injuries.

Evaluation of the analytical and clinical performance of a new high-sensitivity cardiac troponin I assay: hs-cTnI (CLIA) assay

OBJECTIVES

Cardiac troponin (cTn) is the key biomarker for diagnosis of acute coronary syndrome (ACS). We performed a complete assessment of the high-sensitivity cardiac troponin I (hs-cTnI) (CLIA) assay on the analytical performance and clinical diagnostic performance, which was compared with Abbott ARCHITECT hs-cTnI assay.

METHODS

Sex-specific 99th percentile upper reference limits (URLs) were determined from a healthy population of 424 males and 408 females. High-sensitivity performance was assessed by examining the imprecision at sex-specific URLs and the detectable results above LoD in a cohort of healthy population. The diagnostic performance of the hs-cTnI (CLIA) assay was validated in a population of 934 patients with suspected ACS.

RESULTS

The 99th percentile URLs were 15.3 ng/L for female, 31.3 ng/L for male and 24.2 ng/L for overall population. The total imprecision near the sex-specific 99th percentile URLs were <5 %. 76.74 % of females, 97.12 % of males and 86.69 % of overall population had cTnI values exceeding the LoD, which met the criteria of high-sensitivity troponin assay. No cross-reactivity or interference was identified. The diagnostic sensitivity, specificity, PPV, NPV, and AUC of hs-cTnI (CLIA) assay were 97.97 , 90.70, 79.02, 99.21 % and 0.9885, respectively, which were comparable to ARCHITECT hs-cTnI assay.

CONCLUSIONS

hs-cTnI (CLIA) assay is a high-sensitivity troponin I method with high precision, sensitivity and specificity. The clinical diagnostic performance of hs-cTnI (CLIA) is comparable to the established ARCHITECT hs-cTnI assay. Mindray's hs-cTnI (CLIA) assay is an attractive alternative for diagnosis of myocardial infarction with a high level of accuracy and safety.

Flexible-Interval High-Sensitivity Troponin Velocity for the Detection of Acute Coronary Syndromes

Many algorithms for emergency department (ED) evaluation of acute coronary syndrome (ACS) using high-sensitivity troponin assays rely on the detection of a "delta," the difference in concentration over a predetermined interval, but collecting specimens at specific times can be difficult in the ED. We evaluate the use of troponin "velocity," the rate of change of troponin concentration over a flexible short interval for the prediction of major adverse cardiac events (MACEs) at 30 days. We conducted a prospective, observational study on a convenience sample of 821 patients who underwent ACS evaluation at a high-volume, urban ED. We determined the diagnostic performance of a novel velocity-based algorithm and compared the performance of 1- and 2-hour algorithms adapted from the European Society of Cardiology (ESC) using delta versus velocity. A total of 7 of 332 patients (2.1%) classified as low risk by the velocity-based algorithm experienced a MACE by 30 days compared with 35 of 221 (13.8%) of patients classified as greater than low risk, yielding a sensitivity of 83.3% (95% confidence interval [CI] 68.6% to 93.0%) and negative predictive value (NPV) of 97.9% (95% CI 95.9% to 98.9%). The ESC-derived algorithms using delta or velocity had NPVs ranging from 98.4% (95% CI 96.4% to 99.3%) to 99.6% (95% CI 97.0% to 99.9%) for 30-day MACEs. The NPV of the novel velocity-based algorithm for MACE at 30 days was borderline, but the substitution of troponin velocity for delta in the framework of the ESC algorithms performed well. In conclusion, specimen collection within strict time intervals may not be necessary for rapid evaluation of ACS with high-sensitivity troponin.

Outcomes in ED patients with non-specific ECG findings and low high-sensitivity troponin

Background

Although some emergency department risk stratification tools consider non-specific ECG findings as an aid in disposition decisions, their clinical value in patients with an initially low high-sensitivity cardiac troponin I (hsTnI) is unclear.

Objective

Our purpose was to determine if non-specific ECG (ns-ECG) findings are associated with 30-day major adverse cardiac events (MACE) in ED patients presenting with suspected acute coronary syndromes (ACS) who have a low initial hsTnI.

Methods

Using the prospective Siemens Atellica hsTnI Food and Drug Administration submission observational database, we conducted a retrospective cohort study of the association between ns-ECG findings (defined as left bundle branch block [LBBB], ST depression [STD], or T-wave inversions [TWI]) and 30-day MACE (death, myocardial infarction, heart failure hospitalization, or coronary revascularization). Eligible patients presented with suspected ACS to one of 29 US EDs from April 2015 to April 2016, had stable vital signs, a blood sample for hsTnI (Siemen's Atellica, Siemens Healthineers, Inc, Malvern, PA) obtained at 1, 3, and 6 hours after ED presentation, and were followed for 30 days. The relationship between 30-day outcome, initial hsTnI, and ns-ECG was evaluated using chi-square testing.

Results

Of 2676 enrolled, 1313 patients met the inclusion criteria and are included in the analysis. Median (interquartile range) age was 62 years (54, 72), 54% were male, with 56% white, and 39% African American. Median (interquartile range) times from symptom onset to presentation and presentation to specimen collection were 92 (0, 216) and 146 (117, 177) minutes, respectively. The most common presenting symptoms were chest pain (84%), followed by dyspnea (9%). ECG findings were categorized as T-wave inversion or non-specific T wave changes (42%), ST depression ns-ECG ST changes (16%), or LBBB (2%). Thirty-day MACE occurred in 72 (5.5%) patients, with coronary revascularization (35 patients, 2.7%) and heart failure (25 patients, 1.9%) being the most frequent outcomes. In patients with an initial hsTnI below the limit of quantitation (LOQ) of 2.5 ng/L (n = 449), there was no association between ns-ECG changes and 30-day MACE (P = 0.42). If the hsTnI was ≥LOQ (2.5 ng/L), there were increased rates of 30-day MACE and ns-ECG findings (P = 0.01).

Conclusion

In ED suspected ACS patients without unstable vital signs, and an initial hsTnI less than the LOQ (2.5 ng/L), ns-ECG findings are not associated with 30-day major adverse cardiac events. The use of ns-ECG findings in ACS disposition should be considered in the context of hsTnI levels.

Advances in point-of-care testing for cardiovascular diseases

Point-of-care testing (POCT) is a specific format of diagnostic testing that is conducted without accompanying infrastructure or sophisticated instrumentation. Traditionally, such rapid sample-to-answer assays provide inferior analytical performances to their laboratory counterparts when measuring cardiac biomarkers. Hence, their potentially broad applicability is somewhat bound by their inability to detect clinically relevant concentrations of cardiac troponin (cTn) in the early stages of myocardial injury. However, the continuous refinement of biorecognition elements, the optimization of detection techniques, and the fabrication of tailored fluid handling systems to manage the sensing process has stimulated the production of commercial assays that can support accelerated diagnostic pathways. This review will present the latest commercial POC assays and examine their impact on clinical decision-making. The individual elements that constitute POC assays will be explored, with an emphasis on aspects that contribute to economically feasible and highly sensitive assays. Furthermore, the prospect of POCT imparting a greater influence on early interventions for medium to high-risk individuals and the potential to re-shape the paradigm of cardiovascular risk assessments will be discussed.

Outpatient versus observation/inpatient management of emergency department patients rapidly ruled-out for acute myocardial infarction: Findings from the HIGH-US study

BACKGROUND

The actual Emergency Department (ED) dispositions of patients enrolled in observational studies and meeting criteria for rapid acute myocardial infarction (AMI) rule-out are unknown. Additionally, their presenting clinical profiles, cardiac testing/treatments received, and outcomes have not been reported.

METHODS

Patients in the HIGH-US study (29 sites) that ruled-out for AMI using a high-sensitivity cardiac troponin I 0/1-hour algorithm were evaluated. Clinical characteristics of patients having ED discharge were compared to patients placed in observation or hospital admitted (OBS/ADM). Reports of any OBS/ADM cardiac stress test (CST), cardiac catheterization (Cath) and coronary revascularization were reviewed. One year AMI/death and major adverse cardiovascular event rates were determined.

RESULTS

Of the 1,020 ruled-out AMI patients 584 (57.3%) had ED discharge. The remaining 436 (42.7%) were placed in OBS/ADM. Patients with risk factors for AMI, including personal or family history of coronary artery disease, hypertension, previous stroke or abnormal ECG were more often placed in OBS/ADM. 175 (40.1%) had a CST. Of these 32 (18.3%) were abnormal and 143 (81.7%) normal. Cath was done in 11 (34.3%) of those with abnormal and 13 (9.1%) with normal CST. Of those without an initial CST 85 (32.6%) had Cath. Overall, revascularizations were performed in 26 (6.0%) patients. One-year AMI/death rates were low/similar (P = .553) for the groups studied.

CONCLUSIONS

Rapidly ruled-out for AMI ED patients having a higher clinician perceived risk for new or worsening coronary artery disease and placed in OBS/ADM underwent many diagnostic tests, were infrequently revascularized and had excellent outcomes. Alternate efficient strategies for these patients are needed.

The utility of risk scores when evaluating for acute myocardial infarction using high-sensitivity cardiac troponin I

Risk scores including the Thrombolysis in Myocardial Infarction (TIMI) score; History, Electrocardiogram, Age, Risk Factors, and Troponin (HEART) score; and Simplified Emergency Department Assessment of Chest Pain Score (sEDACS) have been used to evaluate patients with symptoms suggestive of acute myocardial infarct (AMI). This study assessed prognostic utility of cardiac risk stratification scores when augmented with a high-sensitivity cardiac troponin-I assay (hs-cTnI).

METHODS

This study enrolled 2,505 suspected AMI patients at 29 hospitals in the United States from April 2015 to April 2016. Blood samples were tested for hs-cTnI on the Atellica IM TnIH Assay (Siemens Healthineers). Patients were considered low risk for death/AMI with a TIMI score = 0, HEART ≤3, sEDACS ≤15, and hs-cTnI <45 ng/L (99th percentile) at time 0 and 2-3 hours.

RESULTS

There were 2,336 patients included after exclusions for ST-segment elevation myocardial infarction or incomplete data. At 30 days, 283 patients (12.1%) had been diagnosed with AMI, and there were 24 (1.0%) deaths and 213 (9.1%) revascularizations. Of 298 patients with death or AMI, 258 (86.6%) had elevated hs-cTnI. The HEART score and sEDACS identified 34.5% and 36.6% of patients as low risk, respectively. This was significantly more than the 12.1% identified by the TIMI score (P < .01).

CONCLUSIONS

The TIMI, HEART, and sEDACS scores all identify low-risk patients when combined with hs-cTnI measurements. The HEART score and sEDACS identified more low-risk patients compared to the TIMI score. These patients could be considered for discharge from the emergency department without further testing.

Ideal high sensitivity troponin baseline cutoff for patients with renal dysfunction

OBJECTIVE

High-sensitivity cardiac troponin assays (hs-cTn) aid in diagnosis of myocardial infarction (MI). These assays have lower specificity for non-ST Elevation MI (NSTEMI) in patients with renal disease. Our objective was to determine an optimized cutoff for patients with renal disease.

METHODS

We conducted an a priori secondary analysis of a prospective FDA study in adults with suspected MI presenting to 29 academic urban EDs between 4/2015 and 4/2016. Blood was drawn 0, 1, 2-3, and 6-9 h after ED arrival. We recorded cTn and estimated glomerular filtrate rate (eGFR) by Chronic Kidney Disease Epidemiology Collaboration equation. The primary endpoint was NSTEMI (Third Universal Definition of MI), adjudicated by physicians blinded to hs-cTn results. We generated an adjusted hscTn rule-in cutoff to increase specificity.

RESULTS

2505 subjects were enrolled; 234 were excluded. Patients were mostly male (55.7%) and white (57.2%), median age was 56 years 472 patients [20.8%] had an eGFR <60 mL/min/1.73 m2. In patients with eGFR <15 mL/min/1.73 m2, a baseline rule-in cutoff of 120 ng/L led to a specificity of 85.0% and Positive Predictive Value (PPV) of 62.5% with 774 patients requiring further observation. Increasing the cutoff to 600 ng/L increased specificity and PPV overall and in every eGFR subgroup (specificity and PPV 93.3% and 78.9%, respectively for eGFR <15 mL/min/1.73m²), while increasing the number (79) of patients requiring observation.

CONCLUSIONS

An eGFR-adjusted baseline rule-in threshold for the Siemens Atellica hs-cTnI improves specificity with identical sensitivity. Further study in a prospective cohort with higher rates of renal disease is warranted.

Performance of Novel High-Sensitivity Cardiac Troponin I Assays for 0/1-Hour and 0/2- to 3-Hour Evaluations for Acute Myocardial Infarction: Results From the HIGH-US Study

STUDY OBJECTIVE

We determine the accuracy of high-sensitivity cardiac troponin I (hs-cTnI), European-derived, rapid, acute myocardial infarction, rule-out/rule-in algorithms applied to a US emergency department (ED) population.

METHODS

Adults presenting to the ED with suspected acute myocardial infarction were included. Plasma samples collected at baseline and between 40 and 90 minutes and 2 and 3 hours later were analyzed in core laboratories using the Siemens Healthineers hs-cTnI assays. Acute myocardial infarction diagnosis was independently adjudicated. The sensitivity, specificity, and negative and positive predictive values for rapid acute myocardial infarction rule-out/rule-in using European algorithms and 30-day outcomes are reported.

RESULTS

From 29 US medical centers, 2,113 subjects had complete data for the 0/1-hour algorithm analyses. With the Siemens Atellica Immunoassay hs-cTnI values, 1,065 patients (50.4%) were ruled out, with a negative predictive value of 99.7% and sensitivity of 98.7% (95% confidence interval 99.2% to 99.9% and 96.3% to 99.6%, respectively), whereas 265 patients (12.6%) were ruled in, having a positive predictive value of 69.4% and specificity of 95.7% (95% confidence interval 63.6% to 74.7% and 94.7% to 96.5%, respectively). The remaining 783 patients (37.1%) were classified as having continued evaluations, with an acute myocardial infarction incidence of 5.6% (95% confidence interval 4.2% to 7.5%). The overall 30-day risk of death or postdischarge acute myocardial infarction was very low in the ruled-out patients but was incrementally increased in the other groups (rule-out 0.2%; continued evaluations 2.1%; rule-in 4.8%). Equivalent results were observed in the 0/2- to 3-hour analyses and when both algorithms were applied to the hs-cTnI ADVIA Centaur measurements.

CONCLUSION

The European rapid rule-out/rule-in acute myocardial infarction algorithm hs-cTnI cut points can be harmonized with a demographically and risk-factor diverse US ED population.

Analytical validation of a highly sensitive point-of-care system for cardiac troponin I determination

Background

Highly sensitive cardiac troponin assays (hs-cTn) are not available as point-of-care (POC) measurements. As rapid testing cannot be achieved at the expense of clinical performance, there is an urgent need to develop and rigorously validate POC hs-cTn. Konica Minolta (KM) has recently developed a surface plasmon-field enhanced fluorescence spectroscopy-based POC hs-cTn I system.

Methods

We validated the analytical characteristics of the KM POC system according to the international guidelines.

Results

Limit of blank (LoB) and limit of detection (LoD) were 0.35 and 0.62 ng/L, respectively, hs-cTn I concentrations corresponding to a total CV of 20%, 10% and 5% were 1.5, 3.9 and 11.0 ng/L, respectively. Method comparison studies showed that KM calibration was successfully traced to higher-order references. Limit of quantitation (LoQ), i.e. the hs-cTn I concentration having a total error of measurement of ≤34%, was 10.0 ng/L. The upper reference limit (URL) for 600 healthy blood donors was calculated at 12.2 ng/L (90% confidence interval [CI]: 9.2–39.2), while sex-partitioned URLs were 20.6 (males) and 10.7 ng/L (females), respectively (p < 0.0001). KM assay measured hs-cTn I concentrations >LoD in 65.7% of all reference individuals, in 76.7% of males and in 54.7% of females, respectively.

Conclusions

The KM system joins the characteristics of POC systems to the analytical performance of hs-cTn.