Effect of Macrotroponin in a Cohort of Community Patients with Elevated Cardiac Troponin

Macrotroponin interference and association with cardiotoxicity in patients receiving cardiotoxic breast cancer therapy: a pilot study

BACKGROUND

Cancer therapy-related cardiac dysfunction (CTRCD) is an important adverse effect in patients receiving potential cardiotoxic cancer therapies. Interpretation of cardiac troponin results can be affected by presence of macrotroponin, which can complicate CTRCD assessment. We aimed to assess whether macrotroponin is detectable in women with ERBB2 + breast cancer receiving sequential therapy with anthracyclines and trastuzumab.

METHODS

A total of 20 serum samples from 12 ERBB2 + breast cancer patients (median age: 55 years, range: 30-69 years) who exhibited a significant increase in high-sensitivity cardiac troponin I (hs-cTnI) from baseline to post-anthracycline (~ 2 months after therapy initiation) and/or 3-months into trastuzumab therapy (~ 5 months after therapy initiation) and/or who had at least one hs-cTnI value above the female-specific 99th percentile (hs-cTnI > 16 ng/L) and had available banked blood for analysis were included in this pilot study. Samples were analyzed using the Abbott STAT High-Sensitive Troponin-I and Roche Elecsys Troponin T hs STAT assays. Macrotroponin was detected by treating the sample with protein G and re-measuring hs-cTn. Macrotroponin presence was defined as a hs-cTnI or hs-cTnT recovery of < 40% or 85%, respectively.

RESULTS

Macrotroponin was not identified after anthracycline treatment but was present in four patients 3-months into trastuzumab therapy, two of which had hs-cTnI concentrations above the 99th percentile. None of these patients exhibited a significant reduction in LVEF and/or GLS despite having significant elevations in hs-cTnI.

CONCLUSIONS

Clinicians should be cautious of benign hs-cTn elevations resulting from macrotroponin presence, as it can complicate CTRCD assessment.

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

BACKGROUND

Cardiac 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.

METHODS

In 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.

RESULTS

In 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.

CONCLUSION

In 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.

Long term false positive hsTnI on Alinity I probably caused by macrotroponin complex: Case report

Elevated troponin levels are often indicative of various cardiac diseases; however, analytical interference can lead to false positive troponin concentrations. We present the case of a 48-year-old female patient with persistently falsely elevated high sensitivity troponin I (hsTnI) probably caused by the presence of macrotroponin. Laboratory testing included determination of hsTnI using various analytical methods, serial dilutions and determination of heterophilic antibodies and other autoimmune antibodies. Only precipitation with polyethylene glycol (PEG) indicated the presence of an interference by causing a significant decrease in hsTnI concentration. Our results suggest that the falsely elevated hsTnI concentration could be due to interference with the macrotroponin complex.

Role of Antitroponin Antibodies and Macrotroponin in the Clinical Interpretation of Cardiac Troponin

Cardiac troponin is extensively used as a biomarker in modern medicine due to its diagnostic capability for myocardial injury, as well as its predictive and prognostic value for cardiac diseases. However, heterophile antibodies, antitroponin antibodies, and macrotroponin complexes can be observed both in seemingly healthy individuals and patients with cardiac diseases, potentially leading to false positive or disproportionate elevation of cTn (cardiac troponin) assay results and introducing discrepancies in clinical interpretations with impact on medical management. In this review article, we describe the possible mechanisms of cTn release and the sources of variations in the assessment of circulating cTn levels. We also explore the pathophysiological mechanisms underlying antitroponin antibody development and discuss the influence exerted by macrotroponin complexes on the results of immunoassays. Additionally, we explore approaches to detect these complexes by presenting various clinical scenarios encountered in routine clinical practice. Finally, unsolved questions about the development, prevalence, and clinical significance of cardiac autoantibodies are discussed.

Prognostic significance of chronic myocardial injury diagnosed by three different cardiac troponin assays in patients admitted with suspected acute coronary syndrome

OBJECTIVES

Chronic myocardial injury (CMI) is defined as stable concentrations of cardiac troponin T or I (cTnT or cTnI) above the assay-specific 99th percentile upper reference limit (URL) and signals poor outcome. The clinical implications of diagnosing CMI are unclear. We aimed to assess prevalence and association of CMI with long-term prognosis using three different high-sensitivity cTn (hs-cTn) assays.

METHODS

A total of 1,292 hospitalized patients without acute myocardial injury had cTn concentrations quantified by hs-cTn assays by Roche Diagnostics, Abbott Diagnostics and Siemens Healthineers. The median follow-up time was 4.1 years. The prevalence of CMI and hazard ratios for mortality and cardiovascular (CV) events were calculated based on the URL provided by the manufacturers and compared to the prognostic accuracy when lower percentiles of cTn (97.5, 95 or 90), limit of detection or the estimated bioequivalent concentrations between assays were used as cutoff values.

RESULTS

There was no major difference in prognostic accuracy between cTnT and cTnI analyzed as continuous variables. The correlation between cTnT and cTnI was high (r=0.724-0.785), but the cTnT assay diagnosed 3.9-4.5 times more patients with having CMI based on the sex-specific URLs (TnT, n=207; TnI Abbott, n=46, TnI Siemens, n=53) and had higher clinical sensitivity and AUC at the URL.

CONCLUSIONS

The prevalence of CMI is highly assay-dependent. cTnT and cTnI have similar prognostic accuracy for mortality or CV events when measured as continuous variables. However, a CMI diagnosis according to cTnT has higher prognostic accuracy compared to a CMI diagnosis according to cTnI.

Practical approaches to the detection of macrotroponin

INTRODUCTION

Macrotroponin is increasingly recognised as a cause of confusion in interpreting high-sensitivity cardiac troponin (hs-cTnI) results. In this study, we sought to evaluate two practical approaches to detecting macrotroponin. These two approaches are PEG precipitation and SVM (support vector machine) analysis to classify discrepancies between hs-cTn assays.

METHOD

Residual serum and heparin plasma specimens (n = 483) with initially elevated hs-cTnI from hospital and community laboratories were retested on multiple hs-cTn platforms before and after PEG precipitation and Protein A immunoglobulin depletion. SVM analysis was conducted to identify a linear equation that best discriminated specimens with macrotroponin using a combination of results from two different hs-cTn assays.

FINDINGS

The diagnostic performance of PEG precipitation was carried out using Protein A immunoglobulin depletion as the reference comparator. When a cutoff residual activity after PEG precipitation of ≤ 20% was used, this threshold carried a high specificity of 92% (confidence interval 83-98%; n = 189) using the Siemens hs-cTnI Vista assay and 95% specificity (86%-98%; n = 242) using the Abbott hs-cTnI Architect assay. SVM analysis generated a linear equation identifying macrotroponin specimens from results obtained on two hs-cTn assays. This approach can be highly specific, comparable to PEG precipitation when certain assay combinations and concentrations are used.

CONCLUSION

We describe and identify practical alternatives to detecting macrotroponin. These approaches can be optimised for high specificity, reducing the need for more complex laboratory methods.

"Troponinosis", the Cardiologist's Curse-When Clinic-Laboratory Interaction Unveils the Mystery: A Case Report

Cardiac troponins are key diagnostic and prognostic biomarkers in acute myocardial infarction and, more generally, for the detection of myocardial injury. Since the introduction of the first immunochemistry methods, there has been a remarkable evolution in analytical performance, especially concerning a progressive improvement in sensitivity. However, the measurement of circulating troponins remains rarely susceptible to analytical interferences. We report a case of persistently elevated troponin I concentrations in a patient with known ischemic heart disease, which almost led to unnecessary diagnostic-therapeutic interventions. A prompt laboratory consultation by the cardiologist ultimately led to the identification of an analytical interference due to troponin macrocomplexes (macrotroponin) causing elevated troponin values in the absence of a clinical presentation compatible with myocardial damage.

Antibody-mediated interferences affecting cardiac troponin assays: recommendations from the IFCC Committee on Clinical Applications of Cardiac Biomarkers

The International Federation of Clinical Chemistry Committee on Clinical Applications of Cardiac Biomarkers (IFCC C-CB) provides educational documents to facilitate the interpretation and use of cardiac biomarkers in clinical laboratories and practice. Our aim is to improve the understanding of certain key analytical and clinical aspects of cardiac biomarkers and how these may interplay. Measurements of cardiac troponin (cTn) have a prominent place in the clinical work-up of patients with suspected acute coronary syndrome. It is therefore important that clinical laboratories know how to recognize and assess analytical issues. Two emerging analytical issues resulting in falsely high cTn concentrations, often several fold higher than the upper reference limit (URL), are antibody-mediated assay interference due to long-lived cTn-antibody complexes, called macrotroponin, and crosslinking antibodies that are frequently referred to as heterophilic antibodies. We provide an overview of antibody-mediated cTn assay interference and provide recommendations on how to confirm the interference and interpret the results.

Methods for analyzing positive cardiac troponin assay interference

OBJECTIVES

The cardiac damage biomarkers cardiac troponin T (cTnT) and troponin I (cTnI) are used to identify patients with myocardial infarction (MI). To make the correct clinical decisions it is important to identify false positive results due to troponin assay interference. Often interferences are caused by high-molecular weight immunocomplexes called macrotroponin that may result in false troponin elevations because of delayed troponin clearance, or heterophilic antibodies that crosslink troponin assay antibodies and generate troponin-independent signals.

DESIGN & METHODS

We describe and compare four methods for cTnI assay interference analysis using a protein G spin column method, gel filtration chromatography and two versions of a sucrose gradient ultracentrifugation for cTnI assay interference analysis on five patients with confirmed cTnI interference and one MI patient without cTnI interference from our troponin interference referral center.

RESULTS

The protein G spin column method had a high between run variability but was still able to identify all five patients with cTnI interference. The sucrose gradient ultracentrifugation methods and the gel filtration method had simlar performancec and correctly identified the immunocomplexes that caused the cTnI interference.

CONCLUSIONS

Our experience is that these methods are sufficient to safely confirm or exclude positive cTnI assay interference.

High-Sensitivity Cardiac Troponin Publications during the COVID-19 Pandemic (2020-2022)

The first publications detailing the clinical utility of high-sensitivity cardiac troponin (hs-cTn) in patients with possible acute coronary syndrome (ACS) are traceable to 2009 [...].