Immunoassay For Cardiac Troponin Research Articles

Exploring strategies to rapidly identify false positives in high-sensitivity cardiac troponin I assay: A prospective study

BackgroundCardiac troponin is the pivotal biomarker of myocardial injury, playing a central role in the diagnosis of acute coronary syndrome and various clinical situations. Nevertheless, challenges arise when patients exhibit elevated cardiac troponin levels in the absence of evident cardiac origin, as evidenced by extensive cardiac exploration, which suggests the presence of an interfering factor. Despite the high performance of high-sensitive cardiac troponin immunoassays, these tests remain susceptible to interferences that may lead to false-positives. MethodsIn the period between July 2021 and July 2024, 8129 patients were hospitalized in the cardiology departments of Bordeaux University Hospital with positive results for high-sensitivity cardiac troponin I. Among them, 15 patients were suspected of having false-positive results, based on clinical and biological observations. ResultsIn this subpopulation, we evaluated prospectively various techniques, including serial dilutions, antibody-binding tubes, and alternative immunoassays (for cardiac troponin I and T) with the objective of identifying any potential analytical interference in their high-sensitive cardiac troponin I measurements. Our investigations revealed that 12 out of 15 suspected cases exhibited an interference on the high-sensitive cardiac troponin I assay. ConclusionIn conclusion, we propose an original algorithm designed to identify high-sensitive cardiac troponin I false-positives. This algorithm can help clinicians to make prompt and informed decisions about patient care, and to avoid erroneous clinical interventions that may result from such interferences.

Photoelectrochemical immunoassay of cardiac troponin I based on ZnTCPP/CdIn2S4 type-II heterojunction and co-catalyzed precipitation biolabeling.

CdIn2S4 and zinc tetrakis(4-carboxyphenyl)porphyrin (ZnTCPP) were synthesized by hydrothermal method, and an organic dye-sensitized inorganic semiconductor ZnTCPP/CdIn2S4 type II heterojunction was constructed on a fluorine-doped tin oxide (FTO) substrate electrode. Asandwich immunostructure forsignal-attenuation photoelectrochemical (PEC) detection of cardiac troponin I (cTnI) was constructed using the ZnTCPP/CdIn2S4/FTO photoanode and a horseradish peroxidase (HRP)-ZnFe2O4-Ab2-bovine serum albumin (BSA) immunolabeling complex. The bioenzyme HRP and the HRP-like nanozyme ZnFe2O4 can co-catalyze the oxidation of 4-chloro-1-naphthol (4-CN) by H2O2 to produce an insoluble precipitate on the photoanode, thus notably reducing the anodic photocurrent for quantitative determination of cTnI. Under the optimal conditions, the photocurrent at 0V vs. SCE in 0.1M phosphate buffer solution (pH 7.40) containing 0.1M ascorbic acid was linear with the logarithm of cTnI concentration from 500fg mL-1 to 50.0 ng mL-1, and the limit of detection (LOD, S/N = 3) is 0.15 pg mL-1. Spiked recoveries were 95.1% ~ 104% for assay of cTnI in human serum samples.

Block-Polymer-Restricted Sub-nanometer Pt Nanoclusters Nanozyme-Enhanced Immunoassay for Monitoring of Cardiac Troponin I.

Noble-metal nanozymes have demonstrated great potential in various fields. However, aggregation of single-particle nanoparticles severely affects their exposed catalytically active sites to the extent of exhibiting weak enzyme-like activity. Here, we present an organic block surfactant (polyvinylpyrrolidone, PVP) to construct monodisperse water-stable Pt nanoclusters (Pt NCs) for an enhanced immunoassay of cardiac troponin I (cTnI). The PVP-modified Pt NC nanozyme exhibited up to 16.3 U mg-1 peroxidase-mimicking activity, which was mainly attributed to the ligand modification on the surface and the electron-absorbing effect of the ligand on the Pt NCs. The PVP-modified Pt NCs have a lower OH-transition potential, as determined by density functional theory. Under optimized experimental conditions, the enhanced nanozyme immunoassay strategy exhibited an ultrawide dynamic response range of 0.005-50 ng mL-1 for cTnI targets with a detection limit of 1.3 pg mL-1, far superior to some reported test protocols. This work provides a designable pathway for the design of artificial enzymes with high enzyme-like activity to further expand the practical range of enzyme alternatives.

One-pot synthesis of AuPt@FexOy nanoparticles with excellent peroxidase-like activity for development of ultrasensitive colorimetric lateral flow immunoassay of cardiac troponin I

Detection of cardiac troponin I (cTnI) plays a critical role in diagnosing acute myocardial infarction (AMI). In this report, a new kind of spherical AuPt@FexOy core@shell nanoparticles (termed as AuPt@FexOy NPs) were one-pot synthesized by a redox interaction-engaged strategy (RIES) without the addition of any surfactants or reducing agents. The as-synthesized AuPt@FexOy NPs not only retain the plasmonic activity of gold nanoparticles (AuNPs), but also possess excellent catalytic activities of platinum nanoparticles (PtNPs) and FexOy nanoclusters. The features of AuPt@FexOy NPs enable greatly enhance the colorimetric detection sensitivity of lateral flow immunoassay (LFIA) through integrating AuPt@FexOy NPs labeling procedure and catalyzing oxidation of chromogenic substrate 3,3',5,5'-tetramethylbenzidine (TMB) signal amplification strategy. The as-developed colorimetric LFIA (termed as AuPt@FexOy-LFIA) exhibits the limit of detection (LOD) as 26.0 pg mL−1 cTnI under the TMB signal amplification mode. In particular, the detection results of cTnI in 40 clinical seral samples by AuPt@FexOy-LFIA are correlated well with those of cTnI in the same samples by commercial enzyme-linked immunosorbent assay (ELISA) detection kit (R2 = 0.97, slope = 1), demonstrating the highly reliable analytical performance and good application prospect of AuPt@FexOy-LFIA.

Automated and rapid chemiluminescence immunoassay for cardiac troponin I based on digital microfluidics

Rapid diagnosis of acute myocardial infarction (AMI) is critical in the clinical setting. An automated and rapid chemiluminescence immunoassay system based on digital microfluidics (DMF) is suggested for cardiac troponin I (cTnI). This method involves a double antibody sandwich structure. The cTnI antigen in the sample to be analyzed was captured by magnetic beads encapsulated with the cTnI antibody, which was subsequently recognized by the biotin-labeled secondary antibody. Horseradish peroxidase (HRP)-labeled streptavidin may be conjugated to biotin and used to mark the cTnI antigen because of the unique way that biotin binds to avidin. The simultaneous recognition of the cTnI antigen by primary and secondary antibodies in sandwich form, as well as the high specificity of the reaction between streptavidin and biotin, considerably improves the sensitivity and specificity of this technique for cTnI detection. This approach has decent stability. For cTnI samples, the full process took 40 min, with a limit of detection (LOD) of 0.34 ng mL−1. Additionally, there was a significant correlation range from 0.39 to 25 ng mL−1, with a correlation value of 0.994. The CV (Coefficient of variation) value was 2.26%. This system is anticipated to be used for the clinical measurement of cTnI in human serum.

Complement C1q in plasma induces nonspecific binding of poly(acrylic acid)-coated upconverting nanoparticle antibody conjugates

Upconverting nanoparticles are attractive reporters for immunoassays, because their high specific activity and lack of autofluorescence background enable their detection at extremely low concentrations. However, the sensitivity achieved with heterogeneous sandwich immunoassays using nanoparticle reporters is generally limited by the nonspecific binding of nanoparticle antibody conjugates to solid supports. In this study, we characterized plasma components associated with elevated nonspecific binding of poly(acrylic acid)-coated upconverting nanoparticles in heterogeneous two-step sandwich immunoassays. Plasma was consecutively fractionated using various chromatographic methods by selecting after each step the fractions producing the highest nonspecific binding of upconverting nanoparticle conjugates in an immunoassay for cardiac troponin I. Finally, the proteins in the fractions associated with highest amount of nonspecific binding were separated by gel electrophoresis and identified with mass spectrometry. The results indicated that complement component C1q was present in the fractions associated with the highest signal from nonspecific binding. The interference was not limited to only poly(acrylic acid)-coated nanoparticles or certain antibody combination, but occurred more generally. The interference was removed by increasing the ionic strength of the assay buffer in the sample incubation step or by adding a negatively charged blocker to bind on positively charged C1q, suggesting that the interaction is mostly electrostatic. Hence, we assume that the interference is likely to affect various negatively charged nanoparticles. The identification of complement component C1q as the major interfering protein allows for more rational design of countermeasures in future immunoassay development utilizing nanoparticle reporters.Graphical abstract

Reagent Filming for Universal Point-of-Care Diagnostics.

Simplifying assays while maintaining the robustness of reagents is a challenge in diagnostics. This problem is exacerbated when translating quality diagnostic assays to developing countries that lack resources and infrastructure such as trained health workers, high-end equipment, and cold-chain systems. To solve this problem, in this study, a simple solution that films assay reagents to simplify the operation of diagnostic assays and preserve the stability of diagnostic reagents without using cold chains is presented. A polyvinyl-alcohol-based water-soluble film is used to encapsulate premeasured and premixed reagents. The reagent film, produced through a simple and scalable cast-drying process, provides a glassy inner matrix with abundant hydroxyl groups that can stabilize various reagents (ranging from chemicals to biological materials) by restricting molecular mobility and generating hydrogen bonds. The reagent film is applied to an enzymatic glucose assay, a high-sensitivity immunoassay for cardiac troponin, and a molecular assay for viral RNA detection, to test its practicability and universal applicability. The film-based assays result in excellent analytical/diagnostic performance and stable long-term reagent storage at elevated temperatures (at 25 or 37°C, for six months), demonstrating clinical readiness. This technology advances the development and distribution of affordable high-quality diagnostics to resource-limited regions.

Label-free electrochemical immunosensor for ultrasensitive determination of cardiac troponin I based on porous fluffy-like AuPtPd trimetallic alloyed nanodendrites

Enhancement in the signals of electrochemical immunosensors via advanced nanomaterials is beneficial for developing immunoassay of cardiac troponin I (cTnI) with high sensitivity and selectivity. By virtue of K3[Fe(CN)6] as a signal probe, an advanced label-free electrochemical immunosensor was fabricated for ultrasensitive detection of cTnI with trimetallic alloyed AuPtPd porous fluffy-like nanodendrites (AuPtPd FNDs), followed by assembly of the antibody (Ab). By virtue of the structural advantages, electronic effects and synergetic catalysis of the trimetals, such nanostructures showed large specific surface area to increase the loading of the cTnI Ab and amplify the electrochemical signals of the probe. The sensor displayed a wide linear range (0.01 ~ 100.0 ng mL−1) and a low detection limit (LOD = 3 pg mL−1) under the optimal conditions, which showed great potential for detecting cTnI in serum samples. Furthermore, this biosensor provides an effective detection platform for analysis of other cardiac markers in practical samples.

Small‐Volume Plasmonic Microwell Array with 3D Hierarchical Nanomaterials for Plasmon‐Enhanced Fluorescence Immunoassay

Developing a small‐volume bioassay using microliter‐scale biofluids is crucial for achieving a rapid, sensitive, and high‐throughput screening and medical diagnosis. Herein, a new plasmonic microwell array (PMA) containing 3D hierarchical nanomaterials for multiplexed bioassays is presented. The microwell array is formed by performing a sequential bottom‐up fabrication involving dispensing UV‐curable photopolymers and plasmonic Ag nanowires (NWs) on a flat substrate. The plasmonic Ag NWs are developed into a multilayer stack of Ag@Au core‐shell NWs having surfaces densely decorated with Au nanoparticles. This multi‐stacked hybrid plasmonic nanostructure provided 3D multiscale hotspots and large effective surfaces for molecular binding sites. Highly improved sensitivities are demonstrated for a plasmon‐enhanced fluorescence‐based immunoassay of cardiac troponin I (cTnI), a diagnostic biomarker for acute myocardial infarction, using a small volume of 5 μL. The limit of detection is determined to be 2.02 pg mL−1 for cTnI, representing a 30‐fold greater sensitivity than the clinical cut‐off value. Furthermore, 3D PMA chips exhibit a highly uniform fluorescence intensity with a coefficient of variation of 3.4%. The 3D PMA provides a sensitive and reliable detection in a high‐throughput manner for point‐of‐care bioanalysis.

Sensitive immunoassay of cardiac troponin I using an optimized microelectrode array in a novel integrated microfluidic electrochemical device.

A sensitive and portable microfluidic electrochemical array device (μFED) was developed for the immunoassay of trace amounts of human cardiac troponin I (cTnI), which is an attractive biomarker for acute myocardial infarction (AMI). The classical "sandwich" method was adopted for the immunoassay. The capture antibody was immobilized using a self-assembled monolayer (SAM) technique, and the process was reorganized to be compatible with the bonding process. The detection antibody was labeled with alkaline phosphatase (AP) for signal amplification. The performance of the μFED was improved by eliminating the shielding effect of the microelectrode array (MEA) integrated in the μFED. The effects of the interstice and the width of the MEA on the response peak current were analyzed and simulated. The concentration gradient, about 3% of the gradient at the surface, was considered as the criterion for estimation of the optimal interstice between electrodes, and its effectiveness was proved. A stable and miniaturized reference electrode was integrated in the μFED, and its potential deviation was less than 5mV in 15min. These efforts resulted in the enhanced immunoassay performance of the μFED. A low limit of detection of about 5pg/mL was obtained in serum samples, and the response current was proportional to the logarithm of concentration from 50pg/mL to 1μg/mL. The immunoassay process was accomplished in 15min. The μFED was thus qualified and is a promising candidate for point-of-care immunoassay of cTnI. Graphical abstract.

Immunoassay for Cardiac Troponin I with Fluorescent Signal Amplification by Hydrolyzed Coumarin Released from a Metal–Organic Framework

Despite its simplicity and specificity, enzyme-linked immunosorbent assay (ELISA) requires conjugation of the enzyme to an antibody and preservation of enzymatic activity during storage and assay. ...

Simple one-pot aqueous synthesis of 3D superstructured PtCoCuPd alloyed tripods with hierarchical branches for ultrasensitive immunoassay of cardiac troponin I

By integrating the amplified electrochemical signals and effective capture of antibodies together, advanced multimetallic superstructured nanocrystals endow label-free immunosensors promising applications in early diagnosis and monitoring of diseases. Herein, four-metallic PtCoCuPd hierarchical branch-like tripods (HBTPs) were directly synthesized by a green one-pot aqueous method without any seed or organic solvent involved, which were applied to construct a novel label-free immunosensor for detecting cardiac troponin I (cTnI). The specific hierarchical micro/nanostructures greatly improved the immobilization of antibodies and enhanced the catalytic activity for K3Fe(CN)6, which would effectively amplify the electrochemical signals, thereby improving the detection sensitivity. Under the optimal conditions, the as-developed immunosensor exhibited a wide linear range (0.001–100.0 ng mL−1) and a low detection limit (0.2 pg mL−1, S/N = 3) for the assay of cTnI. The immunosensor provides a powerful platform for quantitative detection of cTnI, which can be explored to detect other tumor markers in actual sample analysis.

Antibody-Oriented Strategy and Mechanism for the Preparation of Fluorescent Nanoprobes for Fast and Sensitive Immunodetection.

Nanoprobes have been widely used in biomedical engineering. However, antibodies are generally conjugated onto nanoparticles disorderly, which reduces their antigen recognition ability. The existing antibody orientation approaches are usually complex. Here, we developed and demonstrated a simple antibody-oriented strategy for the lateral flow immunoassay of cardiac troponin I by conjugating antibodies onto polystyrene nanospheres at the optimal pH. The binding amount and orientation of antibodies as well as the detection sensitivity were significantly improved. Although pH regulation is commonly used to optimize antibody conjugation, this paper illustrates the mechanism of its antibody orientation enhancement ability for the first time and reveals the important influences of the density, the charge distribution and hydrophilicity of the antibody, the control of the velocities of physical adsorption and chemical coupling, and other factors on antibody orientation. It is of great significance to understand and regulate antibody conjugation on the surface of micro- or nanospheres to construct high-performance probes for in vitro diagnosis applications.

Understanding cardiac troponin biology: all other cardiac biomarkers shall rest in peace?

The concept that high-sensitivity cardiac troponin immunoassays outperform creatine kinase MB (CK-MB) and myoglobin in the diagnostics of acute coronary syndrome has been put forward more than 10 years ago, and is now virtually incontestable. In the seminal study of Keller et al . (1), cardiac troponins, myoglobin and CK-MB were measured in over 1,800 consecutive patients admitted with suspected acute myocardial infarction. In all patients, the diagnostic performance (area under the curve, AUC) of both high-sensitivity cardiac troponin I (cTnI) (AUC, 0.96) and high-sensitivity cardiac troponin T (AUC, 0.85) was found to higher than that of both myoglobin (AUC, 0.82) and CK-MB (AUC, 0.73). Even more importantly, the early (i.e., <3 hours after onset of chest pain) negative and positive predictive values were also higher for high-sensitivity cTnI (0.94 and 0.82, respectively) than for myoglobin (0.87 and 0.64, respectively).

Manganese doped CdS sensitized graphene/Cu2MoS4 composite for the photoelectrochemical immunoassay of cardiac troponin I

As a newly emerged photoactive material, Cu2MoS4 has motivated wide research interests in the field of photoelectrochemistry. Based on manganese doped CdS (CdS:Mn) sensitized graphene (G)/Cu2MoS4 composite, we developed a label-free photoelectrochemical (PEC) immunosensor for the detection of cardiac troponin I (cTnI). G as an excellent 2D conductive material, combined with Cu2MoS4 could improve its charge transfer efficiency. CdS:Mn nanoparticles (NPs) loaded on G/Cu2MoS4 further enlarged the light absorption range of Cu2MoS4 and restrained the electron-hole pairs recombination. Under optimal conditions, the proposed PEC immunosensor responded sensitively to cTnI with a low detection limit of 0.18 pg/mL and a wide linear range (0.005–1000 ng/mL). Moreover, as-fabricated immunosensor also exhibited high sensitivity, excellent selectivity and good stability. This work also was extended to real samples analysis and obtained satisfied results.

A graphene oxide/gold nanoparticle-based amplification method for SERS immunoassay of cardiac troponin I.

Cardiac troponin I (cTnI) was considered as the "gold standard" for acute myocardial infarction (AMI) diagnosis owing to its superior cardiac specificity for cardiac damage and showing little or no changes in patients with a skeletal muscle disease or trauma. Herein, a new signal amplification surface-enhanced Raman scattering (SERS) platform was developed for recognition and detection of cTnI by using gold nanoparticles (AuNPs), graphene oxide (GO) and magnetic beads (MB). Here, antibody/Raman reporter labeled AuNP-functionalized GO were employed as both SERS nanotags and signal amplification carriers. Monoclonal antibody modified MB were applied as the capture probe and separation agents. In the presence of cTnI, sandwich type immunocomplexes, "capture probe/target/SERS nanotags", were formed through antibody-antigen-antibody interactions. Due to the strong SERS enhancement ability of the designed GO/AuNP complexes and a high binding chance between cTnI and the GO/AuNP complexes, the proposed SERS-based immunoassay could selectively detect cTnI with a high sensitivity (detection limit of 5 pg mL-1) and a good linearity was obtained in a range of 0.01-1000 ng mL-1. In addition, this method was also successfully applied for detecting cTnI in serum substitute media with a similar linear range. Furthermore, this strategy can be constructed with different kinds of antibodies and Raman reporters, and thus can be easily used for simultaneous detection of multiple biomarkers. Therefore, this proposed SERS-based signal amplification technique shows strong potential for the clinical diagnosis of AMI disease.

"Ultra-sensitive" cardiac troponins: Requirements for effective implementation in clinical practice.

The measurement of cardiac troponins, either cardiac troponin I or T, has become the culprit of clinical decision making in patients with suspected acute coronary syndrome (ACS), especially in those with non-ST elevation myocardial infarction (NSTEMI). The leading analytical mainstays of cardiac troponin immunoassays include the limit of blank (LoB), limit of detection (LoD), functional sensitivity, the 99th percentile of a healthy reference population, along with the percentage of “ostensibly healthy” subjects displaying measurable values < 99th percentile. The latest generation of cardiac troponin immunoassays, conventionally defined as “high-sensitive” (HS), is characterized by a LoD over 100-fold lower compared to the first commercialized techniques and a percentage of measurable values consistently > 50% in the general healthy population. The very recent commercialization of methods with further improved analytical sensitivity (i.e., “ultra-sensitive” assays), which allow to measure cardiac troponin values in the vast majority of healthy subjects, is now challenging the diagnostic paradigm based on early rule-out of subjects with cardiac troponin values comprised between the 99th percentile and LoD. New diagnostic strategies, entailing assay-specific cut-offs, must hence be developed and validated in large multicenter studies. The aim of this article is to provide an update on commercially available HS and “ultra”-sensitive techniques for measuring cardiac troponins, along with possible implications of increasingly enhanced analytical sensitivity on diagnostic algorithms for evaluating patients with suspected ACS.

A High-Performance Fluorescence Immunoassay Based on the Relaxation of Quenching, Exemplified by Detection of Cardiac Troponin I.

The intramolecular fluorescence self-quenching phenomenon is a major drawback in developing high-performance fluorometric biosensors which use common fluorophores as signal generators. We propose two strategies involving liberation of the fluorescent molecules by means of enzymatic fragmentation of protein or dehybridization of double-stranded DNA. In the former, bovine serum albumin (BSA) was coupled with the fluorescent BODIPY dye (Red BSA), and then immobilized on a solid surface. When the insolubilized Red BSA was treated with proteinase K (10 units/mL) for 30 min, the fluorescent signal was significantly increased (3.5-fold) compared to the untreated control. In the second case, fluorophore-tagged DNA probes were linked to gold nanoparticles by hybridization with capture DNA strands densely immobilized on the surface. The quenched fluorescence signal was recovered (3.7-fold) by thermal dehybridization, which was induced with light of a specific wavelength (e.g., 530 nm) for less than 1 min. We next applied the Red BSA self-quenching relaxation technique employing enzymatic fragmentation to a high-performance immunoassay of cardiac troponin I (cTnI) in a microtiter plate format. The detection limit was 0.19 ng/mL cTnI, and the fluorescent signal was enhanced approximately 4.1-fold compared with the conventional method of direct measurement of the fluorescent signal from a non-fragmented fluorophore-labeled antibody.

Upconverting nanophosphors as reporters in a highly sensitive heterogeneous immunoassay for cardiac troponin I

Photon upconverting nanophosphors (UCNPs) have a unique capability to produce anti-Stokes emission at visible wavelengths via sequential multiphoton absorption upon infrared excitation. Since the anti-Stokes emission can be easily spectrally resolved from the Stokes' shifted autofluorescence, the upconversion luminescence (UCL) is a highly attractive reporter technology for optical biosensors and biomolecular binding assays – potentially enabling unprecedented sensitivity in separation-based solid-phase immunoassays.UCL technology has not previously been applied in sensitive detection of cardiac troponin I (cTnI), which requires highly sensitive detection to enable accurate and timely diagnosis of myocardial infarction. We have developed an UCL-based immunoassay for cTnI using NaYF4: Yb3+, Er3+ UCNPs as reporters. Biotinylated anti-cTnI monoclonal antibody (Mab) and Fab fragment immobilized to streptavidin-coated wells were used to capture cTnI. Captured cTnI was detected from dry well surface after a 15 min incubation with poly(acrylic acid) coated UCNPs conjugated to second anti-cTnI Mab. UCL was measured with a dedicated UCL microplate reader.The UCL-based immunoassay allowed sensitive detection of cTnI. The limit of detection was 3.14 ng L−1. The calibration curve was linear up to cTnI concentration 50,000 ng L−1. Plasma recoveries of added cTnI were 92–117%. Obtained cTnI concentrations from five normal plasma samples were 4.13–10.7 ng L−1 (median 5.06 ng L−1). There is yet significant potential for even further improved limit of detection by reducing non-specifically bound fraction of the Mab-conjugated UCNPs. The assay background with zero calibrator was over 40-fold compared to the background obtained from wells where the reporter conjugate had been excluded.

Fully automated ultrasensitive digital immunoassay for cardiac troponin I based on single molecule array technology.

The association between increases in cardiac troponin and adverse cardiac outcomes is well established. There is a growing interest in exploring routine cardiac troponin monitoring as a potential early indicator of adverse heart health trends. Prognostic use of cardiac troponin measurements requires an assay with very high sensitivity and outstanding analytical performance. We report development and preliminary validation of an investigational assay meeting these requirements and demonstrate its applicability to cohorts of healthy individuals and patients with heart failure. On the basis of single molecule array technology, we developed a 45-min immunoassay for cardiac troponin I (cTnI) for use on a novel, fully automated digital analyzer. We characterized its analytical performance and measured cTnI in healthy individuals and heart failure patients in a preliminary study of assay analytical efficacy. The assay exhibited a limit of detection of 0.01 ng/L, a limit of quantification of 0.08 ng/L, and a total CV of 10% at 2.0 ng/L. cTnI concentrations were well above the assay limit of detection for all samples tested, including samples from healthy individuals. cTnI was significantly higher in heart failure patients, and exhibited increasing median and interquartile concentrations with increasing New York Heart Association classification of heart failure severity. The robust 2-log increase in sensitivity relative to contemporary high-sensitivity cardiac troponin immunoassays, combined with full automation, make this assay suitable for exploring cTnI concentrations in cohorts of healthy individuals and for the potential prognostic application of serial cardiac troponin measurements in both apparently healthy and diseased individuals.