Cardiac troponin testing in the acute care setting: Ordering, reporting, and high sensitivity assays—An update from the Canadian society of clinical chemists (CSCC)

Analytical assessment and performance of the 0/3h algorithm with novel high sensitivity cardiac troponin I

BACKGROUND

Recently, Ortho Clinical Diagnostics have launched a high sensitivity cardiac troponin I assay adapted on Vitros3600 / 5600. We aimed at evaluating the analytical and clinical performances using the 0/3-hour algorithm, of the Ortho hs-cTnI assay on the Vitros 3600® (Ortho Clinical Diagnostics, Illkirch, France) analyzer with comparison to Roche hs-cTnT assay on the Cobas8000/e801® module (Roche diagnostics, Meylan, France) and the Abbott STAT hs-cTnI assay on the Alinity i® (Abbott, Rungis, France) analyzer.

METHODS

Imprecision studies, linearity, limit of detection, and the interference to hemolysis were performed for Ortho hs-cTnI assay. The concordance study was based on results of troponin obtained from 160 patients with chest pain to the emergency department. Testing was performed simultaneously measuring the Roche hs-cTnT and the Ortho hs-cTnI, then on remaining sample the concentration of Abbott hs-cTnI (n = 150). We applied the 0/3h algorithm to rule out/rule in, in acute myocardial infarction.

RESULTS

Analytical performances were acceptable and in accordance with manufacturer's data. For late presenters 100, 92.8 and 88.8% patients could be rule-out with Roche, Ortho and Abbott assay, respectively with one NSTEMI missed with both hs-TnI assays. Applying the hs-cTn cut-offs from 0/3-hour algorithm, 107 (66.8%) could be rule out with Roche hs-cTnT with no AMI missed (sensitivity 100% [95%CI: 90.5 to 100] and NPV 100%); 89 with Ortho hs-cTnI (sensitivity 97.3% [95%CI: 85.8-99.9] and NPV 98.8% [95%CI:92.7-99.8]); and 61 with Abbott hs-cTnI (sensitivity 97% [95%CI: 84.2-99.9] and NPV 98.4% [95%CI: 89.8-99.7]). For rule-in, 23.7% (n = 37) from the total population would be designated in this group, with a specificity of 86.9% (95%CI: 79.7-92.4) and PPV of 69.8% (95%CI: 59.4-78.5) vs specificity of 72.3% (95%CI:63.5-80.0) and PPV of 51.4% (95%CI: 44.1-58.2)with Roche hs-cTnT vs Ortho hs-cTnI respectively; and with Abbott, 33 patients had constitued this group with a specificity of 52.1% (95%CI:42.7-61.4) and PPV of 36.4% (95%CI: 32.0-41.0).

CONCLUSION

In conclusion, according to ESC guidelines, our results indicate that the Ortho hs-cTnI assay for the Vitros 3600 instrument is a method that may be used in the clinical practice using 0/3-hour algorithm.

Clinical Laboratory Practice Recommendations for the Use of Cardiac Troponin in Acute Coronary Syndrome: Expert Opinion from the Academy of the American Association for Clinical Chemistry and the Task Force on Clinical Applications of Cardiac Bio-Markers of the International Federation of Clinical Chemistry and Laboratory Medicine

This document is an essential companion to the third iteration of the National Academy of Clinical Biochemistry [NACB,8 now the American Association for Clinical Chemistry (AACC) Academy] Laboratory Medicine Practice Guidelines (LMPG) on cardiac markers. The expert consensus recommendations were drafted in collaboration with the International Federation of Clinical Chemistry and Laboratory Medicine Task Force on Clinical Applications of Bio-Markers (IFCC TF-CB). We determined that there is sufficient clinical guidance on the use of cardiac troponin (cTn) testing from clinical practice groups. Thus, in this expert consensus document, we focused on clinical laboratory practice recommendations for high-sensitivity (hs)-cTn assays. This document utilized the expert opinion class of evidence to focus on the following 10 topics: (a) quality control (QC) utilization, (b) validation of the lower reportable analytical limits, (c) units to be used in reporting measurable concentrations for patients and QC materials, (d) 99th percentile sex-specific upper reference limits to define the reference interval; (e) criteria required to define hs-cTn assays, (f) communication with clinicians and the laboratory's role in educating clinicians regarding the influence of preanalytic and analytic problems that can confound assay results, (g) studies on hs-cTn assays and how authors need to document preanalytical and analytical variables, (h) harmonizing and standardizing assay results and the role of commutable materials, (i) time to reporting of results from sample receipt and sample collection, and (j) changes in hs-cTn concentrations over time and the role of both analytical and biological variabilities in interpreting results of serial blood collections.

A practical approach for the validation and clinical implementation of a high-sensitivity cardiac troponin I assay across a North American city

Objectives

Despite several publications on the analytical performance of high-sensitivity cardiac troponin (hs-cTn) assays, there has been little information on how laboratories should validate and implement these assays into clinical service. Our study provides a practical approach for the validation and implementation of a hs-cTn assay across a large North American City.

Design and methods

Validation for the Abbott ARCHITECT hs-cTnI assay (across 5 analyzers) consisted of verification of limit of blank (LoB), precision (i.e., coefficient of variation; CV) testing at the reported limit of detection (LoD) and within and outside the 99th percentile, linearity testing, cTnI versus hs-cTnI patient comparison within and between analyzers (Passing and Bablok and non-parametric analyses). Education, clinical communications, and memorandums were issued in advance to inform all staff across the city as well as a selected reminder the day before live-date to important users. All hospitals switched to the hs-cTnI assay concurrently (the contemporary cTnI assay removed) with laboratory staff instructed to repeat samples previously measured with the contemporary cTnI assay with the hs-cTnI assay only by physician request.

Results

Across the 5 analyzers and 6 reagent packs the overall LoB was 0.6 ng/L (n=60) with a CV of 33% at an overall mean of 1.2 ng/L (n=60; reported LoD=1.0 ng/L), with linearity demonstrated from 45,005 ng/L to 1.1 ng/L. Precision testing with a normal patient-pool QC material (mean range across 5 analyzers was 3.9–4.4 ng/L) yielded a range of CVs from 7% to 10% (within-run) and CVs from 7% to 18% (between-run) with the high patient-pool QC material (mean range across 5 analyzers was 29.6–36.3 ng/L) yielding a range of CVs from 2% to 5% (within-run) and CVs from 4% to 8% (between-run). There was agreement between hs-cTnI versus cTnI with the patient samples (slope ranges: 0.89–1.03; intercept ranges: 1.9–3.8 ng/L), however, the median CV on patient samples <100 ng/L across the analyzers was 5.6% for hs-cTnI versus 18.7% for the contemporary assay (p<0.001). Following the switch to hs-cTnI testing, no requests for repeat measurements were received.

Conclusions

Validation and implementation of hs-cTnI testing across multiple sites requires collaboration within the laboratories and between hospital laboratories and clinical staff.

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City-wide analytical validation of a high-sensitivity cardiac troponin assay.

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Practical approach to hs-cTnI validation and clinical implementation.

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Clinical support and communication are important for a successful implementation.

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New QC practices and comparability testing for hs-cTnI monitoring.

Effectiveness of practices for improving the diagnostic accuracy of Non ST Elevation Myocardial Infarction in the Emergency Department: A Laboratory Medicine Best Practices™ systematic review

OBJECTIVES

This article is a systematic review of the effectiveness of four practices (assay selection, decision point cardiac troponin (cTn) threshold selection, serial testing, and point of care testing) for improving the diagnostic accuracy Non-ST-Segment Elevation Myocardial Infarction (NSTEMI) in the Emergency Department.

DESIGN AND METHODS

The CDC-funded Laboratory Medicine Best Practices (LMBP) Initiative systematic review method for quality improvement practices was used.

RESULTS

The current ACC/AHA guidelines recommend using cardiac troponin assays with a 99th percentile upper reference limit (URL) diagnostic threshold to diagnose NSTEMI. The evidence in this systematic review indicates that contemporary sensitive cTn assays meet the assay profile requirements (sensitivity, specificity, PPV, and NPV) to more accurately diagnose NSTEMI than alternate tests. Additional biomarkers did not increase diagnostic effectiveness of cTn assays. Sensitivity, specificity, and NPV were consistently high and low PPV improved with serial sampling. Evidence for use of point of care cTn testing was insufficient to make recommendation, though some evidence suggests that use may result in reduction to patient length of stay and costs.

CONCLUSIONS

Based on the review of and the LMBP(TM) A-6 Method criteria, we recommend the use of cardiac troponin assays without additional biomarkers using the 99th percentile URL as the clinical diagnostic threshold for the diagnosis of NSTEMI. We recommend serial sampling with one sample at presentation and at least one additional second sample taken at least 6h later to identify a rise or fall in the troponin level. No recommendation is made either for or against the use of point of care tests.

DISCLAIMER

The findings and conclusions in this article are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention/the Agency for Toxic Substances and Disease Registry (CDC/ATSDR).

Highly-sensitive troponin I is increased in patients with gynecological cancers

OBJECTIVES

To investigate troponin I (TnI) in patients with gynecological cancers.

METHODS

Highly-sensitive (HS) and conventional TnI were measured in 25 patients with untreated ovarian cancer, 25 with endometriosis and 25 with benign masses.

RESULTS

Both HS and conventional TnI were increase in cancer patients. Values above the cut-off were found in 44% and 16% cancer patients using HS and conventional TnI methods, respectively.

CONCLUSIONS

Cardiac involvement is frequent in patients with gynecological cancers and should be preferably assessed using HS troponin immunoassays.

High Sensitivity Troponins — Translating Research into Practice

Troponin is vital in the evaluation of acute coronary syndrome. Decision limits, based on the 99th percentile upper reference limit derived from a sufficiently large normal reference population, must be determined for each specific troponin method. The new troponins exhibit high-sensitivity performance – assay precision at less than 10% coefficient of variation (at the 99th percentile upper reference limit) and ability to detect measurable values in healthy subjects. The troponin literature has reached a tipping point necessitating guidance on its use from specialist societies.

For a rapid diagnosis of acute myocardial infarction, a sensitive troponin assay is needed in the near-patient testing setting

An early diagnosis of myocardial infarction in the emergency setting would be advantageous for both patients and the physicians treating these patients. Guidelines currently recommend serial samples that are drawn at presentation and 6-9 h later to be measured for cardiac troponin to aid in this diagnosis. However, much effort has been directed to decrease the time to make a diagnosis in this setting, and there has been renewed interest in shortening the time between serial measurements as well as the turnaround time for reporting the results. By eliminating the blood sample transit time to the central laboratory, point-of-care testing or near-patient testing can reduce the turnaround time for reporting the results, however this is possibly at the cost of decreased diagnostic performance. In this article, we discuss the recent results from the RATPAC study, which evaluated whether the combination of myoglobin, the MB isoenzyme of creatine kinase (CKMB) and a sensitive troponin assay would be superior to troponin alone.

Biomarkers for Predicting Serious Cardiac Outcomes at 72 Hours in Patients Presenting Early after Chest Pain Onset with Symptoms of Acute Coronary Syndromes

BACKGROUND

Most outcome studies of patients presenting early to the emergency department with potential acute coronary syndromes have focused on either the index diagnosis of myocardial infarction (MI) or a composite end point at a later time frame (30 days or 1 year). We investigated the performance of 9 biomarkers for an early serious outcome.

METHODS

Patients (n = 186) who presented to the emergency department within 6 h of chest pain onset had their presentation serum sample measured for the following analytes: creatine kinase, creatine kinase isoenzyme MB, enhanced AccuTnI troponin I (Beckman Coulter), high-sensitivity cardiac troponin T (hs-cTnT), ischemia-modified albumin, interleukin-6, investigation use only hs-cTnI (Beckman Coulter), N-terminal pro–B-type natriuretic peptide, and cardiac troponin I (Abbott AxSym). We followed patients until 72 h after presentation and determined whether they experienced the following serious cardiac outcomes: MI, heart failure, serious arrhythmia, refractory ischemic cardiac pain, or death. ROC curves were analyzed to determine the area under the ROC curve (AUC) and optimal cutoffs for the biomarkers.

RESULTS

The AUCs for the hs-cTnI assay (0.86; 95% CI, 0.76–0.96), the AccuTnI assay (0.86; 95% CI, 0.78–0.95), and the hs-cTnT assay (0.82; 95% CI, 0.71–0.94) assays were significantly higher than those for the other 6 assays (AUC values ≤0.71 for the rest of the biomarkers, P &lt; 0.05). The ROC curve–derived optimal cutoffs were ≥19 ng/L (diagnostic sensitivity, 80%; specificity, 88%), ≥0.018 μg/L (diagnostic sensitivity, 75%; specificity, 86%), and ≥32 ng/L (diagnostic sensitivity, 68%; specificity, 92%) for the hs-cTnI, AccuTnI, and hs-cTnT assays, respectively.

CONCLUSIONS

The optimal cutoffs for predicting serious cardiac outcomes in this low-risk population are different from the published 99th percentiles. Larger studies are required to verify these findings.