Clinical performance of a new point-of-care cardiac troponin I assay compared to three laboratory troponin assays☆
Introduction
Measurement of cardiac troponins I and T (cTnI and cTnT) in blood is currently the recommendation for the biochemical identification of patients with myocardial cell injury and AMI [1], [2]. It has recently been shown that the new assays of cTnI and cTnT may be even more sensitive than the previous assays of cTnT (4th generation) early in acute coronary syndrome (ACS) [3], [4], [5], [6]. The introduction of new sensitive assays has led to increased interest in exploring the value of cTnI and cTnT in the acute setting and in particular as point-of care test (POCT) assays.
The cTnI assay developed for the AQT90 FLEX platform (Radiometer Medical ApS, Denmark) is a POCT assay designed to provide a high clinical performance together with a fast turn around time (TAT) with an analytical run time of approximately 18 min. AQT90 FLEX is a random-access point-of-care analyzer intended for the quantitative determination of cardiac, coagulation, and sepsis markers in whole blood or plasma [7].
Current guidelines recommend that that the 99th percentile of the upper reference limit (URL) should be used as a cut-off for the diagnosis of acute myocardial infarction (AMI) [2], [8], given a coefficient of variation (CV) of ≤ 10% at the 99th percentile URL.
The aim of this study was to evaluate the clinical performances of a new POCT assay, the cardiac specific AQT90 FLEX TnI, and to compare it with two sensitive laboratory assays of cTnI, i.e. the Beckman Coulter AccuTnI assay and the Abbott AxSYM ADV assay, as well as the Roche cTnT (4th generation) laboratory assay.
Section snippets
Patient specimens
The study population comprised 458 subjects who were admitted with chest pain and suspected of ACS. The study population included 293 males (64%) and 165 females (36%). Patients were referred by a general practitioner or the ambulance service. They were subsequently admitted and included by the physician on duty. Patients admitted more than once during the investigation period were only included on their first admission. Twelve lead electrocardiogram (ECG-12) was performed in all patients.
Routine diagnostic procedures
At
Results
Of the 458 patients referred with chest-pain, 104 patients (23%) had a final diagnosis of AMI according to the above mentioned criteria. Of these, two patients (1.9%) developed ST segment elevations in the ECG and subsequently went to acute revascularization. The median time fron symptoms onset to the first blood sample was 2.2 h.
Table 1 shows baseline characteristics of the population.
Three assays of cTnI were compared (AQT90 FLEX TnI — designed for quantitative POC testing; Access AccuTnI and
Discussion
Our comparison of three different assays of cTnI against a diagnosis of AMI verified by current diagnostic criteria [2] shows that the three assays behave equally well and with a high degree of sensitivity and specificity. There is a high concordance between the three cTnI assays. Previous studies have showed a low concordance between the Abbott Architect cTnI (which shares antibody configuration with the AxSYM ADV assay used in this study) and the Roche cTnT assays with significantly more
Limitations
The study compares a POC test with laboratory based assays of troponins, and it can therefore be considered a limitation that collection of blood samples and analysis on the AQT90 FLEX instrument was performed by trained laboratory staff and not the staff in the emergency department. Second, one may question that heparinised plasma and not whole blood was used for the POC test. However, the manufacturer authorizes the use of both kinds of specimens without changes in reference values [32].
Conclusion
This study shows that diagnostic performance on admission, with respect to the diagnosis of AMI, of the POCT based AQT90 FLEX TnI was equivalent to the Abbott AxSYM ADV cTnI assay, but inferior to the AccuTnI assay. After 6–9 h, both the central laboratory based assays were superior compared to the AQT90 FLEX TnI POCT assay. The negative predictive value was high for the AQT90 FLEX TnI assay on admission making the assay suitable as a possible rule out marker in the POCT setting. However, this
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Cited by (19)
Clinical performance of cardiac Troponin I: A comparison between the POCT AQT90 FLEX and the Dimension Vista analyzer in an emergency setting
2017, Clinical BiochemistryCitation Excerpt :In particular, the aim of this “protocol study” was to: a) evaluate the analytical performance, in particular the imprecision characteristics, of a “clinically usable” cTnI applied on the point-of-care analyzer AQT90 FLEX; b) evaluate the diagnostic accuracy and compare the clinical performances of the AQT90 FLEX cTnI method with those of the emergency/routine Dimension Vista cTnI assay, in patients presenting to the Emergency Department (ED) with chest pain and suspected acute coronary syndrome (ACS). The AQT90 FLEX analyzer (Radiometer Medical ApS, Bronshoj, Denmark; EC Declaration of Conformity 01/2008 for analyzer and Solution Pack and Troponin I kit) is a random access point-of-care analyzer intended for the quantitative determination of cardiac, coagulation, and sepsis markers in whole blood or plasma [4,5]. It is a fully automatic continuous access analyzer utilizing immunoassay technology and time-resolved fluorometric detection.
Comparison of new point-of-care troponin assay with high sensitivity troponin in diagnosing myocardial infarction
2014, International Journal of CardiologyCitation Excerpt :With the significant differences in analytical characteristics of troponin assays, each assay requires individual assessment. Previously there have been concerns that POC cTn assays lack the analytical sensitivity of laboratory assays, have higher levels of imprecision, lack of concordance with laboratory assays, and variability between assays that results in an overall lower clinical sensitivity for AMI [11–16]. This means that older POC assays carried the disadvantage that a higher proportion of patients with AMI were not detected, either overall or in the early period after onset of symptoms. [10,14,15]
Diagnostic performance of four point of care cardiac troponin I assays to rule in and rule out acute myocardial infarction
2013, Clinical BiochemistryCitation Excerpt :Third, patient serial cTnI data that demonstrate the large variability in individual cTnI concentrations between the different POC assays are shown. Our observations, while representing a small sample population, substantiate the clinical and analytical variability that exists between different POC assays that are available in the marketplace world-wide, along with the prototype GEM Immuno [16,17,21]. The substantial immune-reactivity differences observed in serial cTnI concentrations measured on two representative MI patients by multiple assays (Fig. 1), as well as the substantial differences in clinical sensitivities both at baseline and following presentation (Table 2), are likely predicated on the different analytical sensitivity characteristics for each assay [16,17].
Point-of-care tests in suspected acute myocardial infarction: A systematic review
2013, International Journal of CardiologyCitation Excerpt :Our search yielded 29 studies (15,980 patients): 16 studies on POC TnI and 13 on TnT. In five of the 29 studies (1,747 patients) results were provided or could be recalculated for POC measurements within the time frame of 6 hours, or results were provided with a median time less or equal to 3 hours after onset of symptoms [12–16]. In these studies the positive predictive value (PPV) ranged from 71 to 100%, and the negative predictive value (NPV) from 31 to 90% for predicting presence or absence of AMI (Tables 2 and 4).
Comparison of the new point of care method for measuring cardiac troponin i in whole blood versus two plasma immunoassays
2013, Revista del Laboratorio ClinicoDiagnostic accuracy of a point-of-care troponin i assay for acute myocardial infarction within 3 hours after presentation in early presenters to the emergency department with chest pain
2012, American Heart JournalCitation Excerpt :In our study, this would result in 40 patients with non-MI having a positive Cardio3 TnI. Our study adds value to the current body of literature using POC because it evaluates a new generation of troponin assay with diagnostic performance that appears to be as good or superior to other studies.12-15 We detected no change in diagnostic accuracy between 1.5, 3, and 6 hours of testing..
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Grant support assays and reagents were kindly provided by Abbott Diagnostics, Denmark, Radiometer Medical, Denmark, and Roche Diagnostics, Denmark.