Rapid Rule-Out of Acute Myocardial Injury Using a Single High-Sensitivity Cardiac Troponin I Measurement

Diagnostic performance of Mindray CL1200i high sensitivity cardiac troponin I assay compared to Abbott Alinity cardiac troponin I assay for the diagnosis of type 1 and 2 acute myocardial infarction in females and males: MERITnI study

OBJECTIVES

We examined the 0- and 2-h diagnostic performance of the Mindray high-sensitivity cardiac troponin I (hs-cTnI) assay using two predefined sex-specific 99th percentile upper reference limits (URL) in patients with normal electrocardiograms to aid in the diagnosis of myocardial infarction (MI).

METHODS

Consecutive emergency department patients undergoing serial high-sensitivity cardiac troponin I (hs-cTnI) testing on clinical indication were studied in the 'Mindray hs-cTnI Assay Analytical and Clinical Evaluation for the Diagnosis and RIsk Assessment of Myocardial InfarctIon' (MERITnI) trial (NCT05853042). Plasma hs-cTnI testing was performed using Mindray CL1200i (investigational) and Abbott Alinity (clinical) assays.

RESULTS

In 1,556 patients (60.7 % male, 43.3 % White, 45.8 % Black, 34.8 % chest pain), 2.7 % had type 1 MI, 2.7 % type 2 MI, and 21.5 % non-MI myocardial injury. At 0 h for all MIs (n=86), using package insert URLs and Universal Sample Bank (USB) URLs, sensitivities were 83.7 and 93.0 %. At 0/2 h for all MIs with package insert and USB URLs, sensitivities were higher with serial testing, at 95.3 and 97.7 %. Negative predictive value (NPVs) were excellent and similar for both URLs, ranging from 98 to 100 %. Substantial hs-cTnI concentration differences were observed between sex and injury types. Alinity hs-cTnI diagnostic observations were similar for both package insert and USB URLs.

CONCLUSIONS

The Mindray CL1200i hs-cTnI assay provides the relevant clinical diagnostic information to enable clinicians to deliver cost-effective care for patients to aid in the diagnosis of MI predicated on 0- and 2-h serial testing based on sex-specific 99th percentiles. Novel observations were observed for findings based on different URLs and for females and MI types.

Characterization of Cardiac Troponin Fragment Composition Reveals Potential for Differentiating Etiologies of Myocardial Injury

BACKGROUND

Increased cardiac troponin (cTn) concentrations occur in acute myocardial injury and chronic diseases. Characterization of cTn composition in the circulation may assist in differentiating etiologies of myocardial injury. Our goal was to study cTn composition and kinetics in patients following type 1 myocardial infraction (T1MI), cardiac procedures, and chronic heart diseases to establish the relationship between cTn composition and clinical diagnosis.

METHODS

Plasma samples were collected from 201 patients with T1MI, 78 undergoing cardiac surgeries, and 218 with chronic cardiomyopathy or chronic heart failure. Major cTn forms in the circulation and their ratios were analyzed using cTn composition immunoassays, targeting (a) the long-cTnT cTnI-cTnT-TnC (ITC) ternary complex, short-cTnT ITC complex cleaved at amino acids residues 189-223 of cTnT, and the binary cTnI-TnC (IC) complex, and designated the "high-sensitivity (hs)-cTnI assay;" (b) the long-cTnT ITC complex, and designated the "long-cTnT ITC complex assay;" (c) the long-cTnT ITC complex and short-cTnT ITC complex, and designated the "hs-total ITC complex assay;" and (d) the central part of cTnT of both the long-cTnT ITC complex and free cTnT, and designated the "hs-cTnT assay."

RESULTS

Early-stage T1MI patients showed a high ratio of long-cTnT ITC complex to cTnI (long-cTnT ITC complex/cTnI, R1). Similarly, patients after acute cardiac surgery exhibited increased cTn concentrations with high R1, which decreased rapidly. In chronic disease, cTn composition exhibited stable and low R1 and high ratios of cTnT to cTnI (cTnT/cTnI, R3).

CONCLUSIONS

Kinetic differences in multiple cTn forms contribute to the differentiation between acute injury and chronic disease, with a high proportion of long-cTnT ITC complex implying occurrence of acute injury.

Impact of acute kidney injury on major adverse cardiovascular events in intensive care survivors

Background

Acute kidney injury commonly occurs in patients admitted to ICU. After acute kidney injury, kidney function may not completely recover leading to increased risk of future cardiovascular events. We sought to ascertain the rates of cardiovascular events in ICU survivors and if these rates were affected by the presence of acute kidney injury whilst in ICU.

Methods

This retrospective observational cohort study utilised routinely collected data to identify patients who had survived an admission to one of two ICUs between July 2015 and June 2018. Baseline serum creatinine and subsequent values were used to identify acute kidney injury. Major adverse cardiovascular events described were myocardial injury, coronary artery intervention, or radiological evidence of stroke.

Results

Of the 3994 ICU survivors, major adverse cardiovascular events were identified in 385 patients (9.6%; 95% confidence interval [CI] 8.8-10.6%). Presence of acute kidney injury whilst in ICU was significantly associated with future major adverse cardiovascular events (hazard ratio=1.38; 95% CI 1.12-1.70; P-value=0.003) and future biochemical myocardial injury (hazard ratio=1.48; 95% CI 1.16-1.89; P-value=0.001). Acute kidney injury did not have a statistically significant association with future coronary artery interventions or future cerebrovascular events.

Conclusions

One in 10 ICU survivors experiences a major adverse cardiovascular event after discharge. Acute kidney injury whilst in ICU was associated with an increased risk of major adverse cardiovascular events and specifically myocardial injury. Further research is warranted on whether ICU survivors with acute kidney injury merit enhanced strategies for cardiovascular protection.

High-Sensitivity Cardiac Troponin for Risk Assessment in Patients With Chronic Coronary Artery Disease

BACKGROUND

Cardiac troponin is used for risk stratification of patients with acute coronary syndromes; however, the role of testing in other settings remains unclear.

OBJECTIVES

The aim of this study was to evaluate whether cardiac troponin testing could enhance risk stratification in patients with chronic coronary artery disease independent of disease severity and conventional risk measures.

METHODS

In a prospective cohort of consecutive patients with symptoms suggestive of stable angina attending for outpatient coronary angiography, high-sensitivity cardiac troponin I was measured before angiography, and clinicians were blinded to the results. The primary outcome was myocardial infarction or cardiovascular death during follow-up.

RESULTS

In 4,240 patients (age 66 years [IQR: 59-73 years], 33% female), coronary artery disease was identified in 3,888 (92%) who had 255 (6%) primary outcome events during a median follow-up of 2.4 years (IQR: 1.3-3.6 years). In patients with coronary artery disease, troponin concentrations were 2-fold higher in those with an event compared with those without (6.7 ng/L [IQR: 3.2-14.2 ng/L] vs 3.3 ng/L [IQR: 1.7-6.6 ng/L]; P < 0.001). Troponin concentrations were associated with the primary outcome after adjusting for cardiovascular risk factors and coronary artery disease severity (adjusted HR: 2.3; 95% CI: 1.7-3.0, log10 troponin; P < 0.001). A troponin concentration >10 ng/L identified patients with a 50% increase in the risk of myocardial infarction or cardiovascular death.

CONCLUSIONS

In patients with chronic coronary artery disease, cardiac troponin predicts risk of myocardial infarction or cardiovascular death independent of cardiovascular risk factors and disease severity. Further studies are required to evaluate whether routine testing could inform the selection of high-risk patients for treatment intensification. (Myocardial Injury in Patients Referred for Coronary Angiography [MICA]; ISRCTN15620297).

Rapid diagnostic strategies using high sensitivity troponin assays: what is the evidence and how should they be implemented?

The introduction of high sensitivity measurement of cardiac troponin T (hs cTnT) and cardiac troponin I (hs cTnI) has given the laboratory the ability to measure very low levels of cardiac troponin. The limit of detection of these assays is well below the 99th percentile. These low levels can also be measured with small values of imprecision. A range of algorithms combining presentation measurement with repeat sample intervals of as little as one to 2 hours have been developed. These are able to predict with acceptable accuracy the diagnosis that would be achieved with continued repeat sampling out to six to 12 hours from presentation. In this article, we review the evidence for the diagnostic accuracy of these approaches and the practical aspects of implementation into routine clinical practice.

Rapid Exclusion of Acute Myocardial Injury and Infarction with a Single High Sensitivity Cardiac Troponin T in the Emergency Department: a Multicenter United States Evaluation

BACKGROUND

There are good data to support using a single high-sensitivity cardiac troponin T (hs-cTnT) below the limit of detection (LoD) of 5 ng/L to exclude acute myocardial infarction. Per the United States (US) Food and Drug Administration (FDA), hs-cTnT can only report to the limit of quantitation (LoQ) of 6 ng/L, a threshold for which there is limited data. Our goal was to determine whether a single hs-cTnT below the LoQ of 6 ng/L is a safe strategy to identify patients at low-risk for acute myocardial injury and infarction.

METHODS

The efficacy (proportion identified as low-risk based on baseline hs-cTnT<6 ng/L) of identifying low-risk patients was examined in a multicenter (n=22 sites) US cohort study of emergency department patients undergoing at least one hs-cTnT (CV Data Mart Biomarker cohort). We then determined the performance of a single hs-cTnT<6 ng/L (biomarker alone) to exclude acute myocardial injury (subsequent hs-cTnT >99^th percentile in those with an initial hs-cTnT<6 ng/L). The clinically intended rule-out strategy combining a nonischemic electrocardiogram with a baseline hs-cTnT<6 ng/L was subsequently tested in an adjudicated cohort in which the diagnostic performance for ruling-out acute myocardial infarction and safety (myocardial infarction or death at 30-days) were evaluated.

RESULTS

A total of 85,610 patients were evaluated in the CV Data Mart Biomarker cohort, amongst which 24,646 (29%) had a baseline hs-cTnT<6 ng/L. Women were more likely than men to have hs-cTnT<6 ng/L (38% vs. 20%, p<0.0001). Among 11,962 patients with baseline hs-cTnT<6 ng/L and serial measurements, only 1.2% developed acute myocardial injury, resulting in a negative predictive value of 98.8% (95% CI 98.6, 99.0) and sensitivity of 99.6% (95% CI 99.5, 99.6). In the adjudicated cohort, a nonischemic electrocardiogram with hs-cTnT<6 ng/L identified 33% of patients (610 of 1849) as low-risk and resulted in a negative predictive value and sensitivity of 100% and a 30-day rate of 0.2% for 30-day myocardial infarction or death.

CONCLUSIONS

A single hs-cTnT below the LoQ of 6 ng/L is a safe and rapid method to identify a substantial number of patients at very low risk for acute myocardial injury and infarction.

Diagnostic performance of a rapid, novel, whole blood, point of care high-sensitivity cardiac troponin I assay for myocardial infarction

BACKGROUND

We evaluated the diagnostic performance of a whole blood, point of care (POC) high-sensitivity cardiac troponin I (hs-cTnI) assay for myocardial infarction (MI) compared to central laboratory assays.

METHODS

Consecutive patients presenting to the emergency department with symptoms of ischemia were studied. Serial hs-cTnI testing was based on clinical indication at presentation. Parallel measurements were made using fresh whole blood on Siemens Atellica VTLi POC assay, EDTA plasma on Abbott ARCHITECT i2000 used in practice, and heparin plasma on Siemens Atellica. MI was determined according to the Fourth Universal Definition of MI using 99th percentiles. Sensitivities and negative predictive values (NPV) were calculated using 99th percentile URLs.

RESULTS

1089 Patients, 418 females and 671 males, were enrolled. There were 91 (8.4%) MIs. At baseline (0 h), POC hs-cTnI assay had a sensitivity of 65.7% (95% CI 47.8-80.9) for females and 67.9% (54.0-79.7) for males and NPV of 96.4% (93.9-98.1) for females and 96.7% (94.9-98.0) for males. At 2 h, sensitivity improved to 82.9% (66.4-93.4) for females and 80.4% (67.6-89.8) for males, while NPV improved to 98.2% (96.1-99.3) and 97.9% (96.3-99.0), respectively. For central laboratory assays, comparable diagnostics were observed at 2 h: females - sensitivity 94.3% (80.8-99.3) for ARCHITECT and 79.4% (62.1-91.3) for Atellica, and NPV 99.3% (97.6-99.9) and 98.0% (95.8-99.2), respectively; males - sensitivity 87.5% (75.9-94.8) for ARCHITECT and 80.4% (67.6-89.8) for Atellica, NPVs of 98.7% (97.3-99.5) and 97.9% (96.3-99.0), respectively.

CONCLUSIONS

The POC, whole blood Atellica VTLi hs-cTnI assay demonstrated comparable diagnostic accuracy for MI to central laboratory assays using 99th percentiles.

Age-specific reference values for the 5th generation cardiac troponin T assay in Chinese children

ABSTRACT

The clinical use of the cardiac troponin T (cTnT) assay was limited to the adult population in the diagnosis and prognosis of myocardial injury. However, emerging studies indicated its significant value in the assessment of pediatric cardiology, and it has been routinely measured in most hospitals. Our study investigated the normative values of cTnT in Chinese children and reported the age-specific 99th percentile cut-off for them.A total of 1280 apparently healthy Chinese children were enrolled in our study. Serum levels of cTnT were analyzed on the Roche Elecsys Troponin T Gen 5 STAT assay. According to the Clinical and Laboratory Standards Institute C28-A3 guideline, the 99th percentile upper reference limits (URLs) with 90% confidence intervals (CIs) were calculated in different age subgroups.The 99th percentile URL was 38 (90%CI: 37.0-51.0) ng/L for 1 to <4months old, 26 (90%CI: 25.2-28.5) ng/L for 4 to ≤ 12months old, and 12 (90%CI: 11.1-12.9) ng/L for 1 to 18 years old, respectively. For subjects aged from 1 to 18years, boys had slightly higher cTnT levels than girls (P = .003), while our assay could not measure low cTnT concentrations (≥the limit of detection) in 50% girls.Our study provided age-specific URLs of cTnT for Chinese children, with the 5th generation cTnT assay from Roche Diagnostics. It had significant clinical implications in the interpretation and use of test results for pediatric cardiology.

Cardiac Troponin Thresholds and Kinetics to Differentiate Myocardial Injury and Myocardial Infarction

BACKGROUND

Although the 99th percentile is the recommended diagnostic threshold for myocardial infarction, some guidelines also advocate the use of higher troponin thresholds to rule in myocardial infarction at presentation. It is unclear whether the magnitude or change in troponin concentration can differentiate causes of myocardial injury and infarction in practice.

METHODS

In a secondary analysis of a multicenter randomized controlled trial, we identified 46 092 consecutive patients presenting with suspected acute coronary syndrome without ST-segment-elevation myocardial infarction. High-sensitivity cardiac troponin I concentrations at presentation and on serial testing were compared between patients with myocardial injury and infarction. The positive predictive value and specificity were determined at the sex-specific 99th percentile upper reference limit and rule-in thresholds of 64 ng/L and 5-fold of the upper reference limit for a diagnosis of type 1 myocardial infarction.

RESULTS

Troponin was above the 99th percentile in 8188 patients (18%). The diagnosis was type 1 or type 2 myocardial infarction in 50% and 14% and acute or chronic myocardial injury in 20% and 16%, respectively. Troponin concentrations were similar at presentation in type 1 (median [25th-75th percentile] 91 [30-493] ng/L) and type 2 (50 [22-147] ng/L) myocardial infarction and in acute (50 [26-134] ng/L) and chronic (51 [31-130] ng/L) myocardial injury. The 99th percentile and rule-in thresholds of 64 ng/L and 5-fold upper reference limit gave a positive predictive value of 57% (95% CI, 56%-58%), 59% (58%-61%), and 62% (60%-64%) and a specificity of 96% (96%-96%), 96% (96%-96%), and 98% (97%-98%), respectively. The absolute, relative, and rate of change in troponin concentration were highest in patients with type 1 myocardial infarction (P<0.001 for all). Discrimination improved when troponin concentration and change in troponin were combined compared with troponin concentration at presentation alone (area under the curve, 0.661 [0.642-0.680] versus 0.613 [0.594-0.633]).

CONCLUSIONS

Although we observed important differences in the kinetics, cardiac troponin concentrations at presentation are insufficient to distinguish type 1 myocardial infarction from other causes of myocardial injury or infarction in practice and should not guide management decisions in isolation. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT01852123.

The Best of Both Worlds: Eliminating Creatine Kinase-Muscle/Brain (CK-MB) Testing in the Emergency Department Leads to Lower Costs Without Missed Clinical Diagnoses

The 2014 American Heart Association/American College of Cardiology (AHA/ACC) clinical guidelines recommend cardiac troponin as a superior biomarker to creatine kinase (CK) and creatine kinase-muscle/brain (CK-MB) for the detection of acute coronary syndrome (ACS), namely myocardial infarction and unstable angina. In April 2018, our Emergency Department (ED) transitioned from using standard troponin to using high-sensitivity troponin T, and adopted a clinical guideline consistent with the AHA/ACC. The guideline recommended high-sensitivity troponin T without CK/CK-MB testing in the majority of clinical situations, limiting CK/CK-MB testing to two specific clinical cases: 1) estimated glomerular filtration rate (eGFR) value <15 mL/min, or 2) recent acute coronary syndrome (ACS) event. Per our ED's policy, a "negative" troponin T was defined as being below the limit of detection (LOD) (i.e., <6 ng/L); such a value obtained at least 3 hours after symptom onset "ruled out" an ACS event and did not require a repeat troponin. The goal of this retrospective study was to determine whether the guideline limiting CK-MB testing missed clinically-significant cardiac outcomes (ACS or new diagnosis of coronary artery disease [CAD]) or was associated with mortality. Pre-implementation data (July 1, 2017 - December 31, 2017) was compared with post-implementation data (July 1, 2018 - December 31, 2018). After guideline introduction, CK/CK-MB ordering decreased by nearly 90%, while troponin ordering increased by nearly 20%, likely due to the introduction in June 2018 of high-sensitivity troponin T, which yielded numerous intermediate/indeterminate-range results that prompted repeat testing. Fewer than 1.5% of patients with a "negative" troponin (below the LOD) and a "positive" CK-MB (above the upper limit of normal [ULN]) had ACS or new-diagnosis CAD; patients with either diagnosis did not expire during their hospital stay or within 30 days of their index visit. CK-MB Index, which has a higher specificity than CK, only found ACS or new CAD among 0.8% of positive results. Considering both decreased CK/CK-MB and increased troponin ordering, the net annual direct cost savings in cardiac biomarker testing was extrapolated to $12,700. Had our institution not transitioned to higher cost high-sensitivity troponin ($2.054/unit) from standard troponin ($1.65/unit), and had the rate of troponin ordering increased solely proportionate to the rate of ED visit increase (2% year-over-year) rather than increase nearly 20% (likely due to the transition to high-sensitivity troponin), then the total six-month direct costs on troponin testing would have been $14,632 instead of $21,267.12, and annual direct cost savings would have been $18,945.80 instead of $12,700. The new ED clinical guideline did not result in a significant number of missed ACS or new-diagnosis CAD, and was associated with direct cost savings. These savings probably underestimate total savings, as the reduced number of "false-positive" CK-MB results likely prevented additional costs, such as hospitalization, specialty consultation, coronary calcium CT, echocardiogram, cardiac stress test, and coronary artery catheterization.

High-sensitivity troponin assays for early rule-out of acute myocardial infarction in people with acute chest pain: a systematic review and economic evaluation

BACKGROUND

Early diagnosis of acute myocardial infarction is important, but only 20% of emergency admissions for chest pain will actually have an acute myocardial infarction. High-sensitivity cardiac troponin assays may allow rapid rule out of myocardial infarction and avoid unnecessary hospital admissions.

OBJECTIVES

To assess the clinical effectiveness and cost-effectiveness of high-sensitivity cardiac troponin assays for the management of adults presenting with acute chest pain, in particular for the early rule-out of acute myocardial infarction.

METHODS

Sixteen databases were searched up to September 2019. Review methods followed published guidelines. Studies were assessed for quality using appropriate risk-of-bias tools. The bivariate model was used to estimate summary sensitivity and specificity for meta-analyses involving four or more studies; otherwise, random-effects logistic regression was used. The health economic analysis considered the long-term costs and quality-adjusted life-years associated with different troponin testing methods. The de novo model consisted of a decision tree and a state-transition cohort model. A lifetime time horizon (of 60 years) was used.

RESULTS

Thirty-seven studies (123 publications) were included in the review. The high-sensitivity cardiac troponin test strategies evaluated are defined by the combination of four factors (i.e. assay, number and timing of tests, and threshold concentration), resulting in a large number of possible combinations. Clinical opinion indicated a minimum clinically acceptable sensitivity of 97%. When considering single test strategies, only those using a threshold at or near to the limit of detection for the assay, in a sample taken at presentation, met the minimum clinically acceptable sensitivity criterion. The majority of the multiple test strategies that met this criterion comprised an initial rule-out step, based on high-sensitivity cardiac troponin levels in a sample taken on presentation and a minimum symptom duration, and a second stage for patients not meeting the initial rule-out criteria, based on presentation levels of high-sensitivity cardiac troponin and absolute change after 1, 2 or 3 hours. Two large cluster randomised controlled trials found that implementation of an early rule-out pathway for myocardial infarction reduced length of stay and rate of hospital admission without increasing cardiac events. In the base-case analysis, standard troponin testing was both the most effective and the most costly. Other testing strategies with a sensitivity of 100% (subject to uncertainty) were almost equally effective, resulting in the same life-year and quality-adjusted life-year gain at up to four decimal places. Comparisons based on the next best alternative showed that for willingness-to-pay values below £8455 per quality-adjusted life-year, the Access High Sensitivity Troponin I (Beckman Coulter, Brea, CA, USA) [(symptoms > 3 hours AND < 4 ng/l at 0 hours) OR (< 5 ng/l AND Δ < 5 ng/l at 0 to 2 hours)] would be cost-effective. For thresholds between £8455 and £20,190 per quality-adjusted life-year, the Elecsys® Troponin-T high sensitive (Roche, Basel, Switzerland) (< 12 ng/l at 0 hours AND Δ < 3 ng/l at 0 to 1 hours) would be cost-effective. For a threshold > £20,190 per quality-adjusted life-year, the Dimension Vista® High-Sensitivity Troponin I (Siemens Healthcare, Erlangen, Germany) (< 5 ng/l at 0 hours AND Δ < 2 ng/l at 0 to 1 hours) would be cost-effective.

CONCLUSIONS

High-sensitivity cardiac troponin testing may be cost-effective compared with standard troponin testing.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42019154716.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Evidence Synthesis programme and will be published in full in Health Technology Assessment; Vol. 25, No. 33. See the NIHR Journals Library website for further project information.

Identifying Patients with Low Risk of Acute Coronary Syndrome Without Troponin Testing: Validation of the HEAR Score

BACKGROUND

Current guidelines for patients with suspected acute myocardial infarction are mainly based on troponin testing, commonly requiring an emergency department visit. HEAR score (History, Electrocardiogram, Age, and Risk factors) is a risk stratification tool validated in Europe, deduced from the HEART score (History, Electrocardiogram, Age, Risk factors, and Troponin), already implemented in clinical practice. We aimed to validate the HEAR score to rule out an acute myocardial infarction without needing biomarker testing.

METHODS

Retrospective cohort study at 15 emergency departments between May 2016 and December 2017. All adult encounters evaluated for possible acute myocardial infarction with a physician-documented HEART score for health plan members of Kaiser Permanente Southern California were included. Patients with an ST-segment elevation myocardial infarction, those under hospice care, or with a "do not resuscitate" status were excluded. HEAR scores from 0-8 were calculated for each encounter and used to report 30-day acute myocardial infarction or all-cause mortality for each score.

RESULTS

There were 22,109 patient encounters included in the study. Overall, 30-day acute myocardial infarction or death occurred in 1.1% of patients. Among the 4106 patients (19%) with a HEAR score <2, 3 died and 2 experienced an acute myocardial infarction within 30 days (0.1%; 95% confidence interval, 0.1-0.3). Sensitivity and specificity were 97.9% and 18.8%, respectively.

CONCLUSIONS

A low HEAR score may accurately identify patients with a very low risk of 30-day acute myocardial infarction or death, representing a cohort of patients who might appropriately forego biomarker testing. Future research is warranted to assess the impact of implementing the HEAR score into routine clinical practice.

Time-related performance characteristics of high-sensitivity troponin I assay using manufacturer's controls and reagents

Background

Troponin is a widely used cardiac protein biomarker for acute coronary syndrome. Its increasing importance drives an increasing need to assess, in real-world conditions, the performance of the tests to measure it. We evaluated the performance characteristics of high-sensitivity troponin I assay reagents and ancillary agents on the Abbott ARCHITECT ci4100, ARCHITECT i2000SR and Alinity ci using historical quality control data spanning 5 years.

Design and method

Retrospective diagnostic hs-TnI quality control data were collected between 2015 and 2019 from the Abbott ARCHITECT ci4100, ARCHITECT i2000SR and Alinity ci located in the University College Dublin Clinical Research Centre Core Lab facility. Descriptive statistics for bias and variability were generated. Linear regression models were used to calculate the mean hs-TnI concentrations over Abbott quality control or reagent lot age and over time from the last calibration of the analysers.

Results

Measurement bias on all three systems ranged between -2.49% and 3.98%. The total CV was ≤8.80%, with a within-lot variability for the reagents and controls of ≤5.45% and ≤7.13%, respectively. The between-lot CVs for reagents and controls were ≤7.16% and 6.19%, respectively. The effect of control or reagent age did not greatly affect stability over time. Results were also stable over different times from the last calibration of the analysers.

Conclusion

The results of this study show that the Abbott hs-TnI assay on the ARCHITECT i2000sr and ARCHITECT ci4000 systems is quite stable in a core laboratory environment. The Alinity ci system exhibits similar performance characteristics.

•

Low variability and bias for a high-sensitivity troponin I assay on three Abbott analysers in a core laboratory setting.

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Performance of the high-sensitivity troponin I assay is stable accross the manufacturer’s specified shelf life and over time.

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The manufacturer’s specified calibration window is sufficient for stable high-sensitivity troponin I assay performance.

Independent and combined effects of biotin and hemolysis on high-sensitivity cardiac troponin assays

OBJECTIVES

This study compared the independent and combined effects of hemolysis and biotin on cardiac troponin measurements across nine high-sensitivity cardiac troponin (hs-cTn) assays.

METHODS

Parallel cTn measurements were made in pooled lithium heparin plasma spiked with hemolysate and/or biotin using nine hs-cTn assays: Abbott Alinity, Abbott ARCHITECT i2000, Beckman Access 2, Ortho VITROS XT 7600, Siemens Atellica, Siemens Centaur, Siemens Dimension EXL cTnI, and two Roche Cobas e 411 Elecsys Troponin T-hs cTnT assays (outside US versions, with and without increased biotin tolerance). Absolute and percent cTn recovery relative to two baseline concentrations were determined in spiked samples and compared to manufacturer's claims.

RESULTS

All assays except the Ortho VITROS XT 7600 showed hemolysis and biotin interference thresholds equivalent to or greater than manufacturer's claims. While imprecision confounded analysis of Ortho VITROS XT 7600 data, evidence of biotin interference was lacking. Increasing biotin concentration led to decreasing cTn recovery in three assays, specifically both Roche Cobas e 411 Elecsys Troponin T-hs assays and the Siemens Dimension EXL. While one of the Roche assays was the most susceptible to biotin among the nine studied, a new version showed reduced biotin interference by approximately 100-fold compared to its predecessor. Increasing hemolysis also generally led to decreasing cTn recovery for susceptible assays, specifically the Beckman Access 2, Ortho VITROS XT 7600, and both Roche Cobas e 411 Elecsys assays. Equivalent biotin and hemolysis interference thresholds were observed at the two cTn concentrations considered for all but two assays (Beckman Access 2 and Ortho VITROS XT 7600). When biotin and hemolysis were present in combination, biotin interference thresholds decreased with increasing hemolysis for two susceptible assays (Roche Cobas e 411 Elecsys and Siemens Dimension EXL).

CONCLUSIONS

Both Roche Cobas e 411 Elecsys as well as Ortho VITROS XT assays were susceptible to interference from in vitro hemolysis at levels routinely encountered in clinical laboratory samples (0-3 g/L free hemoglobin), leading to falsely low cTn recovery up to 3 ng/L or 13%. While most assays are not susceptible to biotin at levels expected with over-the-counter supplementation, severely reduced cTn recovery is possible at biotin levels of 10-2000 ng/mL (41-8,180 nmol/L) for some assays. Due to potential additive effects, analytical interferences should not be considered in isolation.

The role of cardiac testing with the 0/1-hour high-sensitivity cardiac troponin algorithm evaluating for acute myocardial infarction

BACKGROUND

The role of cardiac testing in the 3 zones (rule-out, observation, and rule-in) of the 0/1-hour algorithm to evaluate for acute myocardial infarction (AMI) has not been well studied. This study evaluated the 0/1-hour algorithm with a high-sensitivity cardiac troponin (hs-cTnI) assay and investigated cardiac testing in the 3 zones.

METHODS

Patients (n = 552) at a single urban center were enrolled if they were evaluated for AMI. Blood samples were obtained at presentation, 1 hour, and 3 hours for hs-cTnI. Follow-up at 30 to 45 days for death/AMI was done. The results of echocardiograms, stress testing, and coronary angiography were recorded.

RESULTS

In total, 45 (8.2%) had AMI (27 Type 1 and 18 Type 2) during the index hospitalization while at follow-up death/AMI occurred in 11 (2.0%) of patients. The rule-out algorithm had a negative predictive value for AMI of 99.6% while the rule-in zone had a positive predictive value of 56.6%. The MACE rate at follow-up was 0.4% for those in the rule-out group. There were 6/95 (6.3%) abnormal stress tests in the rule-out zone and 4 of these were false positives.

CONCLUSIONS

The 0/1-hour algorithm had high diagnostic sensitivity and negative predictive value for AMI, and adverse events were very low in patients in the rule-out zone. Noninvasive testing in rule-out zone patients had low diagnostic yield.

A Test in Context: Interpretation of High-Sensitivity Cardiac Troponin Assays in Different Clinical Settings

High-sensitivity cardiac troponin (hs-cTn) assays have the ability to detect minute troponin concentrations and resolve minor changes in biomarker concentrations. Clinically, this allows for the ability to rapidly identify or exclude acute myocardial injury in the setting of acute chest discomfort-thus providing more rapid evaluation for acute myocardial infarction-but the improvements in troponin assays also create avenues for other applications where troponin release from the cardiomyocyte might confer prognostic information. These situations include cardiovascular risk assessment across a wide range of clinical circumstances, including apparently-well individuals, those at risk for heart disease, and those with prevalent cardiovascular disorders. The optimal hs-cTn threshold for each circumstance varies by the assay used and by the population assessed. This review will provide context for how hs-cTn assays might be interpreted depending on the application sought, reviewing results from studies leveraging hs-cTn for applications beyond "acute myocardial infarction diagnostic evaluation."

Novel clearance of muscle proteins by muscle cells

Blood levels of cardiac troponins (cTn) and myoglobin are analysed when myocardial infarction (MI) is suspected. Here we describe a novel clearance mechanism for muscle proteins by muscle cells. The complete plasma clearance profile of cTn and myoglobin was followed in rats after intravenous or intermuscular injections and analysed by PET and fluorescence microscopy of muscle biopsies and muscle cells. Compared with intravenous injections, only 5 % of cTnT, 0.6 % of cTnI and 8 % of myoglobin were recovered in the circulation following intramuscular injection. In contrast, 47 % of the renal filtration marker FITC-sinistrin and 81 % of cTn fragments from MI-patients were recovered after intramuscular injection. In addition, PET and biopsy analysis revealed that cTn was taken up by the quadriceps muscle and both cTn and myoglobin were endocytosed by cultured muscle cells. This local clearance mechanism could possibly be the dominant clearance mechanism for cTn, myoglobin and other muscle damage biomarkers released by muscle cells.

Sex-Specific 99th Percentile Upper Reference Limits for High Sensitivity Cardiac Troponin Assays Derived Using a Universal Sample Bank

BACKGROUND

How to select healthy reference subjects in deriving 99th percentiles for cardiac troponin assays still needs to be clarified. To assist with global implementation of high sensitivity (hs)-cardiac troponin (cTn) I and hs-cTnT assays in clinical practice, we determined overall and sex-specific 99th percentiles in 9 hs-cTnI and 3 hs-cTnT assays using a universal sample bank (USB).

METHODS

The Universal Sample Bank (USB) comprised healthy subjects, 426 men and 417 women, screened using a health questionnaire. Hemoglobin A1c (>URL 6.5%), NT-proBNP (>URL 125 ng/L) and eGFR (<60 mL/min), were used as surrogate biomarker exclusion criteria along with statin use. 99th percentiles were determined by nonparametric, Harrell--Davis bootstrap, and robust methods.

RESULTS

Subjects were ages 19 to 91 years, Caucasian 58%, African American 27%, Pacific Islander/Asian 11%, other 4%, Hispanic 8%, and non-Hispanic 92%. The overall and sex-specific 99th percentiles for all assays, before and after exclusions (n = 694), were influenced by the statistical method used, with substantial differences noted between and within both hs-cTnI and hs-cTnT assays. Men had higher 99th percentiles (ng/L) than women. The Roche cTnT and Beckman and Abbott cTnI assays (after exclusions) did not measure cTn values at ≥ the limit of detection in ≥50% women.

CONCLUSIONS

Our findings have important clinical implications in that sex-specific 99th percentiles varied according to the statistical method and hs-cTn assay used, not all assays provided a high enough percentage of measurable concentrations in women to qualify as a hs-assay, and the surrogate exclusion criteria used to define normality tended to lower the 99th percentiles.

High-sensitivity methods for cardiac troponins: The mission is not over yet

The measurement of cardiac troponin (cTn) is recommended by all guidelines as the gold standard for the differential diagnosis of Acute Coronary Syndromes. The aim of this review is to discuss in details some key issues regarding both analytical and clinical characteristics of the high-sensitivity methods for cTn (hs-cTn), which are still considered controversial or unresolved. In particular, the major clinical concern regarding hs-cTn methods is the difficulty to differentiate the pathophysiological mechanism responsible for biomarker release from cardiomyocytes after reversible or irreversible injury, respectively. Indeed, recent experimental and clinical studies have demonstrated that different circulating forms of cTnI and cTnT can be respectively measured in plasma samples of patients with reversible or irreversible myocardial injury. Accordingly, a new generation of hs-Tn methods should be set up, based on immunometric immunoassays or chromatographic techniques, specific for circulating peptide forms more characteristics for reversible or irreversible myocardial injury. It is conceivable that this new generation of hs-cTn methods will complete the mission regarding the laboratory tests for specific cardiac biomarkers, started more than 20 years ago, which has already revolutionized the diagnosis, prognosis and management of patients with cardiac diseases.

A Possible Mechanism behind Faster Clearance and Higher Peak Concentrations of Cardiac Troponin I Compared with Troponin T in Acute Myocardial Infarction

BACKGROUND

Although cardiac troponin I (cTnI) and troponin T (cTnT) form a complex in the human myocardium and bind to thin filaments in the sarcomere, cTnI often reaches higher concentrations and returns to normal concentrations faster than cTnT in patients with acute myocardial infarction (MI).

METHODS

We compared the overall clearance of cTnT and cTnI in rats and in patients with heart failure and examined the release of cTnT and cTnI from damaged human cardiac tissue in vitro.

RESULTS

Ground rat heart tissue was injected into the quadriceps muscle in rats to simulate myocardial damage with a defined onset. cTnT and cTnI peaked at the same time after injection. cTnI returned to baseline concentrations after 54 h, compared with 168 h for cTnT. There was no difference in the rate of clearance of solubilized cTnT or cTnI after intravenous or intramuscular injection. Renal clearance of cTnT and cTnI was similar in 7 heart failure patients. cTnI was degraded and released faster and reached higher concentrations than cTnT when human cardiac tissue was incubated in 37°C plasma.

CONCLUSION

Once cTnI and cTnT are released to the circulation, there seems to be no difference in clearance. However, cTnI is degraded and released faster than cTnT from necrotic cardiac tissue. Faster degradation and release may be the main reason why cTnI reaches higher peak concentrations and returns to normal concentrations faster in patients with MI.

Differences in measurement of high-sensitivity troponin in an on-demand and batch-wise setting

BACKGROUND

Most studies assessing the diagnostic value of high-sensitivity troponin in the diagnosis of myocardial infarction used batch-wise analyses of frozen samples for high-sensitivity troponin measurements. Whether the accuracy of these batch-wise high-sensitivity troponin measurements described in diagnostic studies is comparable to clinical routine is unknown.

METHODS

We enrolled 937 patients presenting with suspected myocardial infarction in this prospective cohort study. Measurements of high-sensitivity troponin I (Abbott Architect) and high-sensitivity troponin T (Roche) were performed in two settings: (a) on-demand in clinical routine using fresh blood samples; and (b) in batches using frozen blood samples from the same individuals at three timepoints (0 hours, 1 hour and 3 hours after presentation).

RESULTS

Median troponin levels were not different between on-demand and batch-wise measurements. Troponin levels in the range of 0 to 40 ng/L showed a very high correlation between the on-demand and batch setting (Pearson correlation coefficient (r) was 0.92-0.95 for high-sensitivity troponin I and 0.96 for high-sensitivity troponin T). However, at very low troponin levels (0 to 10 ng/L) correlation between the two settings was moderate (r for high-sensitivity troponin I 0.59-0.66 and 0.65-0.69 for high-sensitivity troponin T). Application of guideline-recommended rapid diagnostic algorithms showed similar diagnostic performance with both methods.

CONCLUSIONS

Overall on-demand and batch-wise measurements of high-sensitivity troponin provided similar results, but their correlation was moderate, when focusing on very low troponin levels. The application of rapid diagnostic algorithms was safe in both settings.Trial Registration: www.clinicaltrials.gov (NCT02355457).

Evaluation of the Relationship between Early Troponin Clearance and Short-Term Mortality in Patients with Chronic Renal Failure

Objective

In patients with CKD, cTn concentrations may be elevated in the absence of AMI, which is a predicted finding caused by chronic structural heart disease rather than acute injury. The increase in troponin level observed in noncardiac conditions provides conflicting results when predicting mortality. Low lactate clearance was associated with increased mortality. Lactate clearance is calculated as follows: (early lactate - late lactate/early lactate) ∗ 100. We aimed to investigate whether troponin clearance calculated according to this formula had an effect on short-term mortality.

Methods

The study included 300 patients with chronic renal failure who had a sepsis-related organ failure assessment (SOFA) score ≥3. By taking the baseline troponin at the time of emergency presentation as reference and comparing them with the fourth-hour troponin values, troponin clearance was investigated in the evaluation of mortality among hospitalized patients with CKD within the first month after discharge. The data obtained were analyzed using the SPSS data analysis software version 20.0. Student's t-test was used for the parametric data, and the Chi-squared test for the nonparametric data.

Results

Of the 300 patients evaluated, 189 patients survived (mean age 66.20 ± 14.597 years), and 111 died (mean age 74.81 ± 12.916 years). Troponin clearance was detected in 40 of the 111 patients in the mortality group and 119 of the 189 patients in the survival group. Troponin clearance was significantly more frequent in surviving patients (P=0.0000083).

Conclusion

Troponin clearance can be considered as a valuable leading indicator of survival, but higher levels of troponin clearance did not lead to higher survival rates.

[Clinical and Diagnostic Value of Cardiac Markers in Human Biological Fluids]

The article is devoted to problems of clinical-diagnostic value of determination of cardio-specific troponins in human biological fluids. Improvement of laboratory instrumentation and emergence of high sensitivity methods of analysis have allowed to identify troponins in urine, dialysate, and oral fluid. In the review we present actual information related to measurement of troponins in blood serum, data on testing of cardio-specific troponins in urine, dialysate, and oral fluid. Special attention is paid to determination of some cardiomarkers in oral fluid with thorough analysis of diagnostic value and effectiveness of the conducted studies.

High-Sensitivity Troponin and the Application of Risk Stratification Thresholds in Patients With Suspected Acute Coronary Syndrome

BACKGROUND

Guidelines acknowledge the emerging role of high-sensitivity cardiac troponin (hs-cTnl) for risk stratification and the early rule-out of myocardial infarction, but multiple thresholds have been described. We evaluate the safety and effectiveness of risk stratification thresholds in patients with suspected acute coronary syndrome.

METHODS

Consecutive patients with suspected acute coronary syndrome (n=48 282) were enrolled in a multicenter trial across 10 hospitals in Scotland. In a prespecified secondary and observational analysis, we compared the performance of the limit of detection (<2 ng/L) and an optimized risk stratification threshold (<5 ng/L) using the Abbott high-sensitivity troponin I assay. Patients with myocardial injury at presentation, with ≤2 hours of symptoms or with ST-segment elevation myocardial infarction were excluded. The negative predictive value was determined in all patients and in subgroups for a primary outcome of myocardial infarction or cardiac death within 30 days. The secondary outcome was myocardial infarction or cardiac death at 12 months, with risk modeled using logistic regression adjusted for age and sex.

RESULTS

In total, 32 837 consecutive patients (61±17 years, 47% female) were included, of whom 23 260 (71%) and 12,716 (39%) had hs-cTnl concentrations of <5 ng/L and <2 ng/L at presentation. The negative predictive value for the primary outcome was 99.8% (95% CI, 99.7%-99.8%) and 99.9% (95% CI, 99.8%-99.9%) in those with hs-cTnl concentrations of <5 ng/L and <2 ng/L, respectively. At both thresholds, the negative predictive value was consistent in men and women and across all age groups, although the proportion of patients identified as low risk fell with increasing age. Compared with patients with hs-cTnl concentrations of ≥5 ng/L but <99th centile, the risk of myocardial infarction or cardiac death at 12 months was 77% lower in those <5 ng/L (5.3% vs 0.7%; adjusted odds ratio, 0.23 [95% CI, 0.19-0.28]) and 80% lower in those <2 ng/L (5.3% vs 0.3%; adjusted odds ratio, 0.20 [95% CI, 0.14-0.29]).

CONCLUSIONS

Use of risk stratification thresholds for hs-cTnl identify patients with suspected acute coronary syndrome and at least 2 hours of symptoms as low risk at presentation irrespective of age and sex.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT01852123.

Diagnostic Accuracy of a High-Sensitivity Cardiac Troponin Assay with a Single Serum Test in the Emergency Department

OBJECTIVES

We sought to evaluate diagnostic accuracy of a high-sensitivity cardiac troponin I (hs-cTnI) assay for acute coronary syndromes (ACS) in the emergency department (ED). The assay has high precision at low concentrations and can detect cTnI in 96.8% of healthy individuals.

METHODS

In successive prospective multicenter studies (“testing” and “validation”), we included ED patients with suspected ACS. We drew blood for hs-cTnI [Singulex Clarity® cTnI; 99th percentile, 8.67 ng/L; limit of detection (LoD), 0.08 ng/L] on arrival. Patients also underwent hs-cTnT (Roche Elecsys) testing over ≥3 h. The primary outcome was an adjudicated diagnosis of ACS, defined as acute myocardial infarction (AMI; prevalent or incident), death, or revascularization within 30 days.

RESULTS

The testing and validation studies included 665 and 2470 patients, respectively, of which 94 (14.1%) and 565 (22.9%) had ACS. At a 1.5-ng/L cutoff, hs-cTnI had good sensitivity for AMI in both studies (98.7% and 98.1%, respectively) and would have “ruled out” 40.1% and 48.9% patients. However, sensitivity was lower for ACS (95.7% and 90.6%, respectively). At a 0.8-ng/L cutoff, sensitivity for ACS was higher (97.5% and 97.9%, ruling out 28.6% patients in each cohort). The hs-cTnT assay had similar performance at the LoD (24.6% ruled out; 97.2% sensitivity for ACS).

CONCLUSIONS

The hs-cTnI assay could immediately rule out AMI in 40% of patients and ACS in &gt;25%, with similar accuracy to hs-cTnT at the LoD. Because of its high precision at low concentrations, this hs-cTnI assay has favorable characteristics for this clinical application.

Combined testing of copeptin and high-sensitivity cardiac troponin T at presentation in comparison to other algorithms for rapid rule-out of acute myocardial infarction

BACKGROUND

We aimed to directly compare the diagnostic and prognostic performance of a dual maker strategy (DMS) with combined testing of copeptin and high-sensitivity (hs) cardiac troponin T (cTnT) at time of presentation with other algorithms for rapid rule-out of acute myocardial infarction (AMI).

METHODS

922 patients presenting to the emergency department with suspected AMI and available baseline copeptin measurements qualified for the present TRAPID-AMI substudy. Diagnostic measures using the DMS (copeptin <10, <14 or < 20 pmol/L and hs-cTnT≤14 ng/L), the 1 h-algorithm (hs-cTnT<12 ng/L and change <3 ng/L at 1 h), as well as the hs-cTnT limit-of-blank (LoB, <3 ng/L) and -detection (LoD, <5 ng/L) were compared. Outcomes were assessed as combined end-points of death and myocardial re-infarction.

RESULTS

True-negative rule-out using the DMS could be achieved in 50.9%-62.3% of all patients compared to 35.0%, 45.3% and 64.5% using LoB, LoD or the 1 h-algorithm, respectively. The DMS showed NPVs of 98.1%-98.3% compared to 99.2% for the 1 h-algorithm, 99.4% for the LoB and 99.3% for the LoD. Sensitivities were 93.5%-94.8%, as well as 96.8%, 98.7% and 98.1%, respectively. Addition of clinical low-risk criteria such as a HEART-score ≤ 3 to the DMS resulted in NPVs and sensitivities of 100% with a true-negative rule-out to 33.8%-41.6%. Rates of the combined end-point of death/MI within 30 days ranged between 0.2% and 0.3% for all fast-rule-out protocols.

CONCLUSION

Depending on the applied copeptin cut-off and addition of clinical low-risk criteria, the DMS might be an alternative to the hs-cTn-only-based algorithms for rapid AMI rule-out with comparable diagnostic measures and outcomes.

High-Sensitivity Cardiac Troponin-Based Strategies for the Assessment of Chest Pain Patients-A Review of Validation and Clinical Implementation Studies

BACKGROUND

The introduction of high-sensitivity cardiac troponin (hs-cTn) assays has improved the early assessment of chest pain patients. A number of hs-cTn-based algorithms and accelerated diagnostic protocols (ADPs) have been developed and tested subsequently. In this review, we summarize the data on the performance and clinical utility of these strategies.

CONTENT

We reviewed studies investigating the diagnostic and prognostic performance of hs-cTn algorithms [level of detection (LoD) strategy, 0/1-h, 0/2-h, and 0/3-h algorithms) and of hs-cTn-based ADPs, together with the implications of these strategies when implemented as clinical routine. The LoD strategy, when combined with a nonischemic electrocardiogram, is best suited for safe rule-out of myocardial infarction and the identification of patients eligible for early discharge from the emergency department. The 0/1-h algorithms appear to identify most patients as being eligible for rule-out. The hs-cTn-based ADPs mainly focus on prognostic assessment, which is in contrast with the hs-cTn algorithms. They identify smaller proportions of rule-out patients, but there is increasing evidence from prospective studies on their successful clinical implementation. Such information is currently lacking for hs-cTn algorithms.

CONCLUSIONS

There is a trade-off between safety and efficacy for different hs-cTn-based strategies. This trade-off should be considered for the intended strategy, along with its user-friendliness and evidence from clinical implementation studies. However, several gaps in knowledge remain. At present, we suggest the use of an ADP in conjunction with serial hs-cTn results to optimize the early assessment of chest pain patients.

Validation of high-sensitivity performance for a United States Food and Drug Administration cleared cardiac troponin I assay

BACKGROUND

High-Sensitivity (hs) cardiac troponin (cTn) assays are categorized by two criteria: (i) cTn values above the limit of detection (LoD) for >50% of male and female healthy cohorts of ≥300 individuals; (ii) imprecision ≤10% total %CV for sex-specific 99th-percentile clinical decision values (CDVs). No documented hs-Tn assay has yet been FDA-cleared.

METHODS

The PATHFAST cTnI-II assay's LoD was 2.3 ng/L using CLSI EP-17. The AACC Universal Sample Bank of 847 healthy men (50.6%) and women (49.4%) was used to determine 99th-percentile CDVs with Nonparametric, Harrell-Davis and Robust modeling. Health/Medication questionnaires and Amino-terminal proBNP, Hemoglobin A_1c and estimated Glomerular Filtration Rate surrogates excluded underlying health conditions.

RESULTS

The cTnI-II test's total CV was 6.1% at 29 ng/L and 7.1% at 22 ng/L; the LoD was 2.3 ng/L. Of the full 847-member healthy cohort, 113 (13.3%) were excluded by abnormal surrogate biomarkers. The final 734-member healthy population had the following (% > LoD): overall, 487 (66.3%); women, 186 (52.8%); and men, 301 (78.8%). 99th-percentile CDVs by Nonparametric modeling were: 28 ng/L (90% CI: 20-30), overall final 732-member healthy population; 20 ng/L (90% CI: 13-30), 352 women; and 30 ng/L (90% CI: 21-37), 382 men. Differences between sex-specific CDVs were not significantly different (p > .05) with Nonparametric or Harrell-Davis modeling; however, Robust Modeling did show significance (<0.05), with lower CDVs at 11 ng/L (90% CI: 9-12) and 16 ng/L (90% CI: 15-18) for the female and male cohorts, respectively.

CONCLUSIONS

cTnI-II is the only FDA-cleared assay that has demonstrated high-sensitivity cTn assay. Use of recommended modeling in >300 healthy subjects for determining sex-specific 99th-percentile CDVs did not show statistically significant differences except with the Robust modeling.

A Risk Assessment Score and Initial High-sensitivity Troponin Combine to Identify Low Risk of Acute Myocardial Infarction in the Emergency Department

OBJECTIVES

Early discharge of patients with presentations triggering assessment for possible acute coronary syndrome (ACS) is safe when clinical assessment indicates low risk, biomarkers are negative, and electrocardiograms (ECGs) are nonischemic. We hypothesized that the Emergency Department Assessment of Chest Pain Score (EDACS) combined with a single measurement of high-sensitivity cardiac troponin (hs-cTn) could allow early discharge of a clinically meaningful proportion of patients.

METHODS

We pooled data from four patient cohorts from New Zealand and Australia presenting to an emergency department with symptoms suggestive of ACS. The primary outcome was major adverse cardiac events (MACE) within 30 days of presentation. In patients with a nonischemic ECG we evaluated the sensitivity for MACE and percentage low risk of every combination of high-sensitivity cardiac troponin T (hs-cTnT) concentration and high-sensitivity cardiac troponin I (hs-cTnI) concentration with EDACS. We used a standard smoothing technique on the probability density function for hs-cTn and EDACS and applied bootstrapping to determine the optimal threshold combinations, namely, the combination that maximized the percentage low risk with ≥98.5% sensitivity for MACE.

RESULTS

From 2,536 patients, 2,258 presented without an ischemic ECG of whom 272 (12.1%) had a MACE within 30 days. The optimal threshold for hs-cTnI was 7 ng/L combined with an EDACS threshold of 16 (36.8% patients low risk). The optimal thresholds for hs-cTnT were 8 ng/L combined with an EDACS threshold of 15 (30.2% patients low risk).

CONCLUSION

Single measurements of both hs-cTnI and hs-cTnT at presentation combined with EDACS to identify over 30% of patients as low risk and therefore eligible for safe early discharge after only one blood draw.

Renal Dysfunction Influences the Diagnostic and Prognostic Performance of High-Sensitivity Cardiac Troponin I

Measures of cardiac troponin (cTn) may have lower specificity for myocardial infarction in patients with CKD. We examined the diagnostic accuracy of baseline and serial high-sensitivity cTnI (hs-cTnI) measurements for myocardial infarction and 30- and 180-day mortality according to renal function. hs-cTnI was measured (Abbott assay) using sex-specific 99th percentiles (women, 16 ng/L; men, 34 ng/L) in 1555 adults presenting to the emergency department with symptoms suggesting ischemia (NCT02060760). Myocardial infarction was adjudicated along universal definition classification. Renal function did not significantly affect sensitivity or negative predictive values. Specificity decreased with impaired renal function from 93%-95% with normal function (eGFR≥90 ml/min per 1.73 m2; n=722) to 57%-61% with severely impaired renal function (eGFR<30 ml/min per 1.73 m2; n=81) and 40%-41% on dialysis (n=78). Positive predictive values decreased with decreasing renal function from 51%-57% with normal function to 27%-42% with severely impaired function and 15%-32% on dialysis. Receiver operating characteristic curve areas trended lower at baseline and 3 hours with renal impairment. Mortality increased significantly with increasing hs-cTnI tertile (1.3%, 6.0%, and 10.4%, respectively). Patients with hs-cTnI concentration exceeding concentrations in the 99th percentiles had a mortality rate (11.7%) significantly higher than that of patients with concentrations between 99th percentile concentrations and limit of detection (6.2%) or below limit of detection (1.1%). Renal dysfunction and dialysis reduced the rule-in performance but not the rule-out performance of hs-cTnI for myocardial infarction, and mortality increased in patients with higher hs-cTnI concentrations and any level of renal dysfunction.

High-Sensitivity Cardiac Troponin and the Risk Stratification of Patients With Renal Impairment Presenting With Suspected Acute Coronary Syndrome

BACKGROUND

High-sensitivity cardiac troponin testing may improve the risk stratification and diagnosis of myocardial infarction, but concentrations can be challenging to interpret in patients with renal impairment, and the effectiveness of testing in this group is uncertain.

METHODS

In a prospective multicenter study of consecutive patients with suspected acute coronary syndrome, we evaluated the performance of high-sensitivity cardiac troponin I in those with and without renal impairment (estimated glomerular filtration rate <60mL/min/1.73m2). The negative predictive value and sensitivity of troponin concentrations below the risk stratification threshold (5 ng/L) at presentation were reported for a primary outcome of index type 1 myocardial infarction, or type 1 myocardial infarction or cardiac death at 30 days. The positive predictive value and specificity at the 99th centile diagnostic threshold (16 ng/L in women, 34 ng/L in men) was determined for index type 1 myocardial infarction. Subsequent type 1 myocardial infarction and cardiac death were reported at 1 year.

RESULTS

Of 4726 patients identified, 904 (19%) had renal impairment. Troponin concentrations <5 ng/L at presentation identified 17% of patients with renal impairment as low risk for the primary outcome (negative predictive value, 98.4%; 95% confidence interval [CI], 96.0%-99.7%; sensitivity 98.9%; 95%CI, 97.5%-99.9%), in comparison with 56% without renal impairment (P<0.001) with similar performance (negative predictive value, 99.7%; 95% CI, 99.4%-99.9%; sensitivity 98.4%; 95% CI, 97.2%-99.4%). The positive predictive value and specificity at the 99th centile were lower in patients with renal impairment at 50.0% (95% CI, 45.2%-54.8%) and 70.9% (95% CI, 67.5%-74.2%), respectively, in comparison with 62.4% (95% CI, 58.8%-65.9%) and 92.1% (95% CI, 91.2%-93.0%) in those without. At 1 year, patients with troponin concentrations >99th centile and renal impairment were at greater risk of subsequent myocardial infarction or cardiac death than those with normal renal function (24% versus 10%; adjusted hazard ratio, 2.19; 95% CI, 1.54-3.11).

CONCLUSIONS

In suspected acute coronary syndrome, high-sensitivity cardiac troponin identified fewer patients with renal impairment as low risk and more as high risk, but with lower specificity for type 1 myocardial infarction. Irrespective of diagnosis, patients with renal impairment and elevated cardiac troponin concentrations had a 2-fold greater risk of a major cardiac event than those with normal renal function, and should be considered for further investigation and treatment.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT01852123.

Patient selection for high sensitivity cardiac troponin testing and diagnosis of myocardial infarction: prospective cohort study

Objective To evaluate how selection of patients for high sensitivity cardiac troponin testing affects the diagnosis of myocardial infarction across different healthcare settings.Design Prospective study of three independent consecutive patient populations presenting to emergency departments.Setting Secondary and tertiary care hospitals in the United Kingdom and United States.Participants High sensitivity cardiac troponin I concentrations were measured in 8500 consecutive patients presenting to emergency departments: unselected patients in the UK (n=1054) and two selected populations of patients in whom troponin testing was requested by the attending clinician in the UK (n=5815) and the US (n=1631). The final diagnosis of type 1 or type 2 myocardial infarction or myocardial injury was independently adjudicated.Main outcome measures Positive predictive value of an elevated cardiac troponin concentration for a diagnosis of type 1 myocardial infarction.Results Cardiac troponin concentrations were elevated in 13.7% (144/1054) of unselected patients, with a prevalence of 1.6% (17/1054) for type 1 myocardial infarction and a positive predictive value of 11.8% (95% confidence interval 7.0% to 18.2%). In selected patients, in whom troponin testing was guided by the attending clinician, the prevalence and positive predictive value were 14.5% (843/5815) and 59.7% (57.0% to 62.2%) in the UK and 4.2% (68/1631) and 16.4% (13.0% to 20.3%) in the US. Across both selected patient populations, the positive predictive value was highest in patients with chest pain, with ischaemia on the electrocardiogram, and with a history of ischaemic heart disease.Conclusions When high sensitivity cardiac troponin testing is performed widely or without previous clinical assessment, elevated troponin concentrations are common and predominantly reflect myocardial injury rather than myocardial infarction. These observations highlight how selection of patients for cardiac troponin testing varies across healthcare settings and markedly influences the positive predictive value for a diagnosis of myocardial infarction.

Diagnostic Performance of High Sensitivity Compared with Contemporary Cardiac Troponin I for the Diagnosis of Acute Myocardial Infarction

BACKGROUND

We examined the diagnostic performance of high-sensitivity cardiac troponin I (hs-cTnI) vs contemporary cTnI with use of the 99th percentile alone and with a normal electrocardiogram (ECG) to rule out acute myocardial infarction (MI) and serial changes (deltas) to rule in MI.

METHODS

We included consecutive patients presenting to a US emergency department with serial cTnI onclinical indication. Diagnostic performance for acute MI, including MI subtypes, and 30-day outcomes were examined.

RESULTS

Among 1631 patients, MI was diagnosed in 12.9% using the contemporary cTnI assay and in 10.4% using the hs-cTnI assay. For ruling out MI, contemporary cTnI ≤99th percentile at 0, 3, and 6 h and a normal ECG had a negative predictive value (NPV) of 99.5% (95% CI, 98.6–100) and a sensitivity of 99.1% (95% CI, 97.4–100) for diagnostic and safety outcomes. Serial hs-cTnI measurements ≤99th percentile at 0 and 3 h and a normal ECG had an NPV and sensitivity of 100% (95% CI, 100–100) for diagnostic and safety outcomes. For ruling in MI, contemporary cTnI measurements had specificities of 84.4% (95% CI, 82.5–86.3) at presentation and 78.7% (95% CI, 75.4–82.0) with serial testing at 0, 3, and 6 h, improving to 89.2% (95% CI, 87.1–91.3) by using serial cTnI changes (delta, 0 and 6 h) &gt;150%. hs-cTnI had specificities of 86.9% (95% CI, 85.1–88.6) at presentation and 85.7% (95% CI, 83.5–87.9) with serial testing at 0 and 3 h, improving to 89.3% (95% CI, 87.3–91.2) using a delta hs-cTnI (0 and 3 h) &gt;5 ng/L.

CONCLUSIONS

hs-cTnI and contemporary cTnI assays are excellent in ruling out MI following recommendations predicated on serial testing and the 99th percentile with a normal ECG. For ruling in MI, deltas improve the specificity. ClinicalTrials.gov Identifier: NCT02060760

Single High-Sensitivity Cardiac Troponin I to Rule Out Acute Myocardial Infarction

BACKGROUND

This study examined the performance of single high-sensitivity cardiac troponin I (hs-cTnI) measurement strategies to rule out acute myocardial infarction.

METHODS

This was a prospective, observational study of consecutive patients presenting to the emergency department (n = 1631) in whom cTnI measurements were obtained using an investigational hs-cTnI assay. The goals of the study were to determine 1) negative predictive value (NPV) and sensitivity for the diagnosis of acute myocardial infarction, type 1 myocardial infarction, and type 2 myocardial infarction; and 2) safety outcome of acute myocardial infarction or cardiac death at 30 days using hs-cTnI less than the limit of detection (LoD) (<1.9 ng/L) or the High-STEACS threshold (<5 ng/L) alone and in combination with normal electrocardiogram (ECG).

RESULTS

Acute myocardial infarction occurred in 170 patients (10.4%), including 68 (4.2%) type 1 myocardial infarction and 102 (6.3%) type 2 myocardial infarction. For hs-cTnI<LoD (27%), the NPV and sensitivity for acute myocardial infarction were 99.6% (95% confidence interval 98.9%-100%) and 98.8 (97.2%-100%). For hs-cTnI<5 ng/L (50%), the NPV and sensitivity for acute myocardial infarction were 98.9% (98.2%-99.6%) and 94.7% (91.3%-98.1%). In combination with a normal ECG, 1) hs-cTnI<LoD had an NPV of 99.6% (98.9%-100%) and sensitivity of 99.4% (98.3%-100%); and 2) hs-cTnI<5 ng/L had an NPV of 99.5% (98.8%-100%) and sensitivity of 98.8% (97.2%-100%). The NPV and sensitivity for the safety outcome were excellent for hs-cTnI<LoD alone or in combination with a normal ECG, and for hs-cTnI<5 ng/L in combination with a normal ECG.

CONCLUSION

Strategies using a single hs-cTnI alone or in combination with a normal ECG allow the immediate identification of patients unlikely to have acute myocardial infarction and who are at very low risk for adverse events at 30 days.