The 99th percentile and imprecision of point-of-care cardiac troponin I in comparison to central laboratory tests in a large reference population

Analytical verification of the Atellica VTLi point of care high sensitivity troponin I assay

OBJECTIVES

The Siemens Point-of-Care Testing (POC) Atellica® VTLi high-sensitivity troponin I (hsTnI) device has been previously validated. Verification independently provides evidence that an analytical procedure fulfils concordance with laboratory assays, imprecision, and hemolysis interference requirements.

METHODS

Five whole blood samples spanning the measuring interval were analysed 20 times in succession. Hemolysis interference was assessed at three troponin concentrations by spiking five hemolysate concentrations to plasma to achieve free hemoglobin concentrations 35-1,000 mg/dL. Concordance between whole blood (VTLi) and plasma on laboratory analysers (Beckman, Roche, Siemens) was assessed by Pearson correlation and kappa statistics at the (LOQ) and upper reference limit (URL). This was repeated for frozen plasma samples.

RESULTS

Coefficients of variation for whole blood were <10 % for whole blood troponin concentrations of 9.2 and 15.9 ng/L, thus below the URL. Hemolysis positively interfered; at 250 mg/dL affecting the low troponin sample (+3 ng/L; +60 %) and high troponin sample (+37 ng/L; +24 %). Correlation coefficients were 0.98, 0.90 and 0.97 between VTLi and Beckman, Roche and Siemens assays respectively. Corresponding kappa statistics were 0.80, 0.73 and 0.84 at the LOQ and 0.70, 0.44 and 0.67 at the URL.

CONCLUSIONS

Concordances between VTLi and laboratory assays were at least non-inferior to those between laboratory assays. Imprecision met manufacturer claims and was consistent with a high sensitivity assay. There is potential for hemolysis interference, highlighting the need for quality samples. The results support performance characteristics previously reported in validation studies, and the device offers acceptable performance for use within intended medical settings.

Recent advances in cardiac biomarkers detection: From commercial devices to emerging technologies

Although cardiac pathologies are the major cause of death in the world, it remains difficult to provide a reliable diagnosis to prevent heart attacks. Rapid patient care and management in emergencies are critical to prevent dramatic consequences. Thus, relevant biomarkers such as cardiac troponin and natriuretic peptides are currently targeted by commercialized Point-Of-Care immunoassays. Key points still to be addressed concern cost, lack of standardization, and poor specificity, which could limit the reliability of the assays. Consequently, alternatives are emerging to address these issues. New probe molecules such as aptamers or molecularly imprinted polymers should allow a reduction in cost of the assays and an increase in reproducibility. In addition, the assay specificity and reliability could be improved by enabling multiplexing through the detection of several molecular targets in a single device.

Cardiac biomarker measurement by point of care testing - Development, rationale, current state and future developments

Cardiac biomarker measurements are integral to the diagnosis and management of patients presenting with breathlessness and chest pain. Measurement of B type natriuretic peptide either directly or of the N-terminal portion of the prohormone although possible by point of care testing (POCT) has largely become a laboratory test. Measurement of the cardiac troponins cardiac troponin T (cTnT) and cardiac troponin I (cTnI) can easily and accurately be performed by POCT. The situation has been complicated by the development of high sensitivity assays for cTnT and cTnI and the subsequent development of rapid rule out algorithms allowing patient categorisation and discharge on admission and 1 to 2 h following admission. This article reviews the development of POCT for cardiac biomarkers, the evidence base comparing POCT with central laboratory testing, its strengths and limitations, and how POCT fits into the world of high sensitivity troponin assays. It also discusses what evidence there is that POCT can form part of rapid decision-making strategies and how this applies in an era of algorithms based on and is derived from measurement of high sensitivity troponin in the central laboratory.

How to choose a point-of-care testing for troponin

BACKGROUND

Point-of-care (POC) cTn assays are needed when the central laboratory is unable to provide timely results to the emergency department. Many POC devices are available. The prospect of choosing them is daunting. In order to provide a quick decision-making reference for POC cTn device selection comparing them to the central laboratory, seven POC devices commonly employed by emergency department were evaluated.

METHODS

Firstly, we reviewed all devices package inserts. Secondly, we evaluated several POC cTn assays for imprecision, linearity, and correlation with central laboratory assays according to CLSI EP protocols. The linear regression analyses were performed only for the detectable concentrations. Five cTnI devices (Alere Triage, BioMerieux Vidas, Mitsubishi Pathfast, ReLIA TZ-301, and Radiometer AQT90) were evaluated against a contemporary cTnI assay (Beckman Access II Accu TnI). Two cTnT assays (Radiometer AQT90 and Roche Cobas h232) were compared to a high-sensitivity (hs) cTnT method (Roche Cobas e601).

RESULTS

For cTn levels around the 99th percentile upper reference limits (URLs) of the comparator assays, imprecision could not be assessed for the Alere, BioMerieux, and Cobas h232 as they gave undetectable readings due to a lack of assay sensitivity. Imprecision (CV) was unacceptably high for the ReLIA (33.3%). On account of this precision metric, these four assays were deemed unsuitable. Regression analyses showed acceptable linearity for all the POC devices. The correlation coefficients for ReLIA, BioMerieux, Cobas h232, and Radiometer cTnT were >0.95. Unlike the cTnT devices, the cTnI assays employ different capture and detection antibodies leading to non-commutable results. The POC cTn results were concordant with their comparator-Radiometer cTnT 90%, Pathfast cTnI 85%, and Radiometer cTnI 75%.

CONCLUSION

Our study provides the procedure and essential data to guide selection of a POC cTn device. Of the point-of-care devices, methods evaluated Radiometer AQT90 (cTnI and cTnT) and Pathfast might be considered.

Performance Evaluation of Cardiac Troponin I Assay: A Comparison Between the Point-of-care Testing Radiometer AQT90 FLEX and the Central Laboratory Siemens Advia Centaur Analyzer

Background

To validate the point of care testing (POCT) Trop-I analyzer and compare it with a central laboratory-based chemiluminescence immunoassay, in order to evaluate its performance for use in critical care areas. Moreover, for clinical decision-making, it is imperative to know the extent to which patient stratification will differ based on the analytic method being used. In particular, the aim of this study was to evaluate the analytical performance of the point-of-care analyzer and demonstrate the agreement with the central laboratory measurements in patients presenting to the emergency department (ED) with chest pain and suspected acute coronary syndrome (ACS).

Methods

This cross-sectional study was performed at the section of chemical pathology, department of pathology and laboratory medicine, the Aga Khan University (AKU), Karachi, from October to November 2017. Samples from patients and the quality control material of Trop-I were analyzed for imprecision, linearity, and method comparison on Advia Centaur (Siemens Diagnostics, CA, USA), and the AQT90 FLEX analyzer (Radiometer Medical ApS, Brønshøj, Denmark) with photometric detection at the section of chemical pathology, AKU. Statistical analysis was done using Microsoft Excel (Microsoft Corporation, Washington, United States) and EP Evaluator version 10.3.0.556 (Data Innovations, LLC, VT, US). Quantitative variables were represented in terms of mean ± SD. For precision, the computed SD was compared with allowable random error. Furthermore, Cohen’s kappa was applied to observe the agreement between the two methods.

Results

The Trop-I Precision study on the POCT analyzer showed a coefficient of variation (CV) of 2.4% using a pooled patient sample with a mean Trop-I of 2.15 ± 0.05 ng/ml. Three standards ranging from 0.034 to 1.316 ng/ml were run in triplicate to verify accuracy and linearity. The allowable systematic error (SEa) was 10.0%. The maximum deviation for a mean recovery from 100% was 4.1%. All three of the mean recoveries were accurate and within the allowable error limits. The results were linear with slope 1.04, intercept 0.0. On a method comparison, Trop-I showed good agreement, yielding a kappa value of 0.95.

Conclusion

This study has validated the performance of a POCT Trop-I assay against a central laboratory immunoassay and found acceptable results. POCT assays for cTnI should be implanted in emergency settings to ensure the fast triage of patients with chest pain, as well as timely diagnosis.