Statin-induced immune mediated necrotising myopathy presenting with a markedly elevated cardiac troponin T in the absence of myocardial injury

Cardiac troponin (cTn) is a sensitive test to assess for myocardial injury. However certain clinical situations can result in a raised cTn in the absence of cardiac involvement. Here we present a case of a 65-year-old woman on long term atorvastatin who presented with generalised weakness, non-specific chest pain, and a persistently elevated high sensitivity cardiac troponin T. Upon further investigation acute myocardial injury was excluded and a diagnosis of statin-induced immune mediated necrotising myopathy (IMNM) was made. The patient improved with cessation of atorvastatin and initiation of immunosuppressive therapy with mycophenolate, intravenous immunoglobulin, and steroids. The mechanism for cTn elevation in skeletal myopathies without cardiac damage and the presentation and treatment of statin-induced IMNM are reviewed. We highlight the importance that in these cases the true cause of the raised cTn is recognised to allow prompt diagnosis and treatment of the underlying myopathy.

Differences in Cardiac Troponin T Composition in Myocardial Infarction and End-Stage Renal Disease Patients: A Blood Tube Effect?

BACKGROUND

Cardiac troponin T (cTnT) is key in diagnosing myocardial infarction (MI) but is also elevated in end-stage renal disease (ESRD) patients. Specific larger cTnT proteoforms were identified for the acute phase of MI, while in serum of ESRD patients solely small cTnT fragments were found. However, others allocated this to a pre-analytic effect due to abundant thrombin generation in serum. Therefore, we investigated the effect of various anticoagulation methods on cTnT composition and concentration and compared the cTnT composition of MI and ESRD patients.

METHODS

The agreement of cTnT concentrations between simultaneously collected serum, lithium-heparin (LH) plasma, and ethylenediaminetetraacetic acid (EDTA) plasma was studied using the high-sensitivity (hs-)cTnT immunoassay. cTnT proteoform composition was investigated in a standardized time-dependent manner through spike experiments and in simultaneously collected blood matrixes of MI and ESRD patients.

RESULTS

Excellent hs-cTnT concentration agreements were observed across all blood matrixes (slopes > 0.98; 95% CI, 0.96-1.04). Time-dependent degradation (40 kDa intact:29 kDa fragment:15 to 18 kDa fragments) was found in LH plasma and EDTA plasma, and serum in ratios (%) of 90:10:0, 0:5:95, and 0:0:100, respectively (48 h after blood collection). Moreover, gel filtration chromatography (GFC) profiles illustrated mainly larger cTnT proteoforms in MI patients, while in ESRD patients mainly 15 to 18 kDa fragments were found for all matrices.

CONCLUSIONS

The extent of cTnT degradation in vitro is dependent on the (anti)coagulation method, without impacting hs-cTnT concentrations. Furthermore, mainly larger cTnT proteoforms were present in MI patients, while in ESRD patients mainly small 15 to 18 kDa cTnT fragments were found. These insights are essential when developing a novel hs-cTnT assay targeting larger cTnT proteoforms.

Establishment of a microspheres-based homogeneous fluorescence immunoassay for the rapid detection of cardiac troponin I

Myocardial infarction occurs rapidly, and thus the rapid detection of cTnI levels is the key to its diagnosis. Most current assays take 10-30 min. In this study, we developed a method for accurately measuring cardiac troponin I (cTnI) levels in human sera with amplified luminescence neighborhood homogeneous assay (AlphaLISA). The method involves coupling two cTnI antibodies targeting different epitopes to the surface of carboxylated donor and acceptor beads. The final signal values were detected by the double-antibody sandwich method, and the best reaction conditions were obtained by optimizing the experimental conditions. The sensitivity, specificity, accuracy, and precision of the method were evaluated. Results showed that the method requires only 3 min to produce the results, the detection sensitivity is 27.06 ng L-1, and the measurement range is 34.56-62 500 ng L-1. cTnI-AlphaLISA has an intra-assay precision of 2.18-4.57% (<10%) and an inter-assay precision of 5.60-6.95% (<10%). The relative recovery rates are within reasonable limits. In addition, the serum assay results of the method were compared with chemiluminescence immunoassay, and the results are in agreement with one another (ρ = 0.8803; P < 0.0001). The method is expected to be developed as a routine method, but further studies and evaluations are needed.

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.

Macrotroponins cause discrepancy in high-sensitivity examination

AIM

We present two cases with clearly discrepant results of clinical examination and cardiac troponin I (cTnI) and cardiac troponin T (cTnT) concentrations. In similar cases with discrepant results, the possibility of interference should be considered.

METHODS

Due to the suspicion of the presence of macrotroponin I in both of the presented cases, the patients were invited to our laboratory and both cTnI (Architect i1000, Abbott) and cTnT (Cobas 8000, Roche) concentrations were analysed. The samples were treated by preincubation in a heterophilic antibodies blocking tube (HBT) and analysed. Precipitation with polyethylene glycol solution (PEG) and molecular weight separation by gel filtration on Sephadex G100 was performed and concentrations of cTnI were analysed.

RESULTS

In the same blood sample, the cTnT and cTnI concentrations were 7 and 1782 ng/L, respectively, in Case 1, and 6 and 96 ng/L, respectively, in Case 2. Incubation of samples in HBT had no significant effect. CTnI concentrations after precipitation with PEG - presented as the percentage of initial concentrations - were 7.4% in Case 1 (and 26.8% in the control sample) and 1.4% in Case 2 (and 56.0% in the control sample). These results indicate a significant decrease in both cases, supporting presence of macrotroponin I. Finally, analyses of cTnI concentrations after gel filtration also supported the presence of macrotroponin I.

CONCLUSION

The present cases show that the presence of macrotroponin can lead to unnecessary investigation of the patient. When the possibility of interference is suspected, cooperation with laboratory staff to help with interpretation or to perform more detailed analysis is crucial.

Clinical Biochemistry of Serum Troponin

Accurate measurement and interpretation of serum levels of troponin (Tn) is a central part of the clinical workup of a patient presenting with chest pain suspicious for acute coronary syndrome (ACS). Knowledge of the molecular characteristics of the troponin complex and test characteristics of troponin measurement assays allows for a deeper understanding of causes of false positive and false negative test results in myocardial injury. In this review, we discuss the molecular structure and functions of the constituent proteins of the troponin complex (TnT, TnC, and TnI); review the different isoforms of Tn and where they are from; survey the evolution of clinical Tn assays, ranging from first-generation to high-sensitivity (hs); provide a primer on statistical interpretation of assay results based on different clinical settings; and discuss potential causes of false results. We also summarize the advances in technologies that may lead to the development of future Tn assays, including the development of point of care assays and wearable Tn sensors for real-time continuous measurement.

Implementation of the European Society of Cardiology 0/3-hour accelerated diagnostic protocol, using high sensitive troponin T: a clinical practice evaluation of safety and effectiveness involving 3003 patients with suspected acute coronary syndrome

BACKGROUND

There have been relatively few studies detailing the real-world effectiveness and safety of accelerated diagnostic protocols (ADP), using high sensitivity cardiac troponin (hs-cTn).

OBJECTIVE

To analyse the safety and effectiveness of early emergency department (ED) discharge following implementation of the European Society of Cardiology (ESC) 0/3-hour ADP for suspected acute coronary syndromes (ACS).

METHOD

We prospectively studied 2 cohorts of consecutive suspected ACS presentations to ED before (n=1642) and after (n=1376, 2 centres) implementation of the ESC 0/3-hour ADP incorporating limit of detection rule out. Safety was defined by MACE (major adverse cardiac events) inclusive of type 1 myocardial infarction (MI) in patients discharged from ED, and clinical effectiveness by percentage ED discharge. Continuous variables and categorical data were evaluated by independent t-test and χ2 test, respectively. Time-to-event data were analysed as survival data and converted to Kaplan-Meier curves for interpretation.

RESULTS

In the preimplementation period, there was a higher prevalence of MI. Discharge from ED increased by >100% (from 27.1% to 56.5% of the cohort) with no safety signal (MACE rate 4/444 (0.9%) vs 4/769 (0.52%), p=0.430 for the 2011 and 2018 cohort, respectively). This correlated with a marked reduction in length of stay overall but a more modest reduction for those discharged from ED (6 hours 10 min vs 5 hours 25 min, p<0.001) for the 2011 and 2018 cohort, respectively. There were improvements in presentation to blood draw (163-90 min, p<0.001). Time from presentation to first ECG actually increased (16.2 vs 31.2 min, p<0.001). Analysis of hs-cTn values and ECGs revealed a maximum ED discharge rate of 69%, by applying the 0/3-hour protocol, implying potential for increasing safe ED discharge.

CONCLUSIONS

Implementation of an ADP with hs-cTn is safe and effective for early rule-out and discharge of suspected ACS but require considerable resources and education to optimise maximal patient flow.

Elevated high-sensitivity cardiac troponin T serum concentration in subjects with spinal cord injury

BACKGROUND

The biochemical analysis of high-sensitivity cardiac troponins (hs-cTn) from peripheral blood specimens has been established as biomarker for myocardial injury. Independently of myocardial injury, increased serum hs-cTn concentrations have been described in patients with myopathies. The relevance and frequency of noncardiac hs-cTn elevations in spinal cord injury (SCI) is unknown. Our study aimed to 1) determine the frequency of increased hs-cTn concentrations of supposedly noncardiac origin above the 99th percentile (upper reference limit, URL) in an unselected SCI population and 2) compare the two protagonist analytes cTnT and cTnI with respect to these noncardiac elevations.

METHODS

In this monocentric, cross-sectional study, we sampled blood from n = 30 SCI subjects without cardiac symptoms to test for hs-cTnT and hs-cTnI serum concentrations.

RESULTS

18/30 (60%) of SCI subjects showed increased hs-cTnT concentrations above the URL of 14 ng/l (p < 0.001). In 4 subjects (22.2%) concentrations were >50 ng/l. Moreover, 3 of these four subjects fulfilled the 6-h troponin dynamics criterion for acute myocardial injury in serial hs-cTnT testing. In contrast, no subject demonstrated increased hs-cTnI concentrations according to the URL of 40 ng/l. 6-h troponin dynamics were also unremarkable for hs-cTnI testing.

CONCLUSIONS

SCI subjects frequently have increased hs-cTnT concentrations without clinical and hs-cTnI evidence of myocardial injury. Clinicians must be aware of cTnT "skeletal muscle false-positives" in SCI, which applies to elevated baseline cTnT concentrations and troponin dynamics in serial measurements. In case of diagnostic uncertainty, simultaneous analysis of cTnI might be helpful.

Assay interference as a cause of false positive troponin T elevation in emergency department patients

BACKGROUND

Troponin assays are used in the diagnosis of myocardial injury and may show elevated results for a variety of reasons. However it is increasingly recognised that cardiac troponin elevation may in some cases be due to assay interference. This is of significant importance as a misdiagnosis of myocardial injury may lead to unnecessary and potentially harmful investigation and treatment for patients. We sought to confirm the accuracy of cardiac high sensitivity troponin T (chsTnT) elevation in an unselected group of patients presenting to the emergency department, by using a second confirmatory cardiac high sensitivity troponin I (chsTnI) assay.

METHODS

We identified patients presenting to two local emergency departments over a five-day period who had chsTnT levels measured as part of routine clinical care. All samples with elevated chsTnT levels (above the 99% centile URL) were retested for chsTnI in order to confirm true myocardial injury.

RESULTS

A total of 74 samples from 54 patients were analysed for chsTnT and chsTnI. 7 samples (9.5%) had chsTnI levels < 5 ng/L suggesting assay interference as the cause of chsTnT elevation.

CONCLUSIONS

Assay interference leading to false positive troponin elevation may be more common than many physicians appreciate and can potentially lead to harmful investigation and treatment for patients. In cases where the diagnosis of myocardial injury is uncertain, a second alternative troponin assay should be performed to confirm true myocardial injury.

"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.

Cardiomuscular Biomarkers in the Diagnosis and Prognostication of Immune Checkpoint Inhibitor Myocarditis

BACKGROUND

Immune checkpoint inhibitors (ICIs) are approved for multiple cancers but can result in ICI-associated myocarditis, an infrequent but life-threatening condition. Elevations in cardiac biomarkers, specifically troponin-I (cTnI), troponin-T (cTnT), and creatine kinase (CK), are used for diagnosis. However, the association between temporal elevations of these biomarkers with disease trajectory and outcomes has not been established.

METHODS

We analyzed the diagnostic accuracy and prognostic performances of cTnI, cTnT, and CK in patients with ICI myocarditis (n=60) through 1-year follow-up in 2 cardio-oncology units (APHP Sorbonne, Paris, France and Heidelberg, Germany). A total of 1751 (1 cTnT assay type), 920 (4 cTnI assay types), and 1191 CK sampling time points were available. Major adverse cardiomyotoxic events (MACE) were defined as heart failure, ventricular arrhythmia, atrioventricular or sinus block requiring pacemaker, respiratory muscle failure requiring mechanical ventilation, and sudden cardiac death. Diagnostic performance of cTnI and cTnT was also assessed in an international ICI myocarditis registry.

RESULTS

Within 72 hours of admission, cTnT, cTnI, and CK were increased compared with upper reference limits (URLs) in 56 of 57 (98%), 37 of 42 ([88%] P=0.03 versus cTnT), and 43 of 57 ([75%] P<0.001 versus cTnT), respectively. This increased rate of positivity for cTnT (93%) versus cTnI ([64%] P<0.001) on admission was confirmed in 87 independent cases from an international registry. In the Franco-German cohort, 24 of 60 (40%) patients developed ≥1 MACE (total, 52; median time to first MACE, 5 [interquartile range, 2-16] days). The highest value of cTnT:URL within the first 72 hours of admission performed best in terms of association with MACE within 90 days (area under the curve, 0.84) than CK:URL (area under the curve, 0.70). A cTnT:URL ≥32 within 72 hours of admission was the best cut-off associated with MACE within 90 days (hazard ratio, 11.1 [95% CI, 3.2-38.0]; P<0.001), after adjustment for age and sex. cTnT was increased in all patients within 72 hours of the first MACE (23 of 23 [100%]), whereas cTnI and CK values were less than the URL in 2 of 19 (11%) and 6 of 22 (27%) of patients (P<0.001), respectively.

CONCLUSIONS

cTnT is associated with MACE and is sensitive for diagnosis and surveillance in patients with ICI myocarditis. A cTnT:URL ratio <32 within 72 hours of diagnosis is associated with a subgroup at low risk for MACE. Potential differences in diagnostic and prognostic performances between cTnT and cTnI as a function of the assays used deserve further evaluation in ICI myocarditis.

High sensitivity troponins: A potential biomarkers of cardiovascular risk for primary prevention

There have been several approaches to building charts for CV risk, all of which have both strengths and limitations. Identifying early organ damage provides relevant information and should be included in risk charts, although the direct relationship with risk is imprecise, variability between operators at the time to assess, and low availability in some healthcare systems, limits its use. Biomarkers, like troponin (cTns) isoforms cTnI and cTnT, a cardiac specific myocyte injury marker, have the great advantage of being relatively reproducible, more readily accessible, and applicable to different populations. New and improved troponin assays have good analytical performance, can measure very low levels of circulating troponin, and have low intra individual variation, below 10 %. Several studies have analyzed the blood levels in healthy subjects and their predictive value for cardiovascular events in observational, prospective and post-hoc studies. All of them offered relevant information and shown that high sensitivity hs-cTnI has a place as an additional clinical marker to add to current charts, and it also reflects sex- and age-dependent differences. Although few more questions need to be answered before recommend cTnI for assessing CV risk in primary prevention, seems to be a potential strong marker to complement CV risk charts.

The false positive troponin results: case studies of analytical interference

Cardiac troponin I and T are particularly sensitive and specific markers for cardiomyocyte damage. Myocardial injury can occur due to a discrepancy between oxygen supply and demand (eg coronary artery occlusion and arrhythmias), other cardiac causes (eg pericarditis, myocarditis, cardiac surgery, cardioversion etc) or systemic conditions (eg sepsis, stroke and chronic renal disease). The latest European Society of Cardiology guidelines help to guide clinicians through these different causes. Occasionally troponin concentrations may not fit the clinical presentation and, therefore, other aetiologies should be considered. An under-appreciated basis of a high troponin concentration is a false positive result, which can be attributable to analytical interference from components in the patient's blood. Uncovering this interference can be pivotal to avoid unnecessary and potentially harmful investigations or treatment for patients. We present two cases of false positive troponin results caused by analytical interference. The normal reference range for the assay (Access; Beckman Coulter, High Wycombe, UK) used at our organisation is 0-18 ng/L.

Use of high-sensitivity cardiac troponins in the emergency department for the early rule-in and rule-out of acute myocardial infarction without persistent ST-segment elevation (NSTEMI) in Italy

Serial measurements of cardiac troponin are recommended by international guidelines to diagnose myocardial infarction (MI) since 2000. However, some relevant differences exist between the three different international guidelines published between 2020 and 2021 for the management of patients with chest pain and no ST-segment elevation. In particular, there is no agreement on the cut-offs or absolute change values to diagnose non-ST-segment elevation MI (NSTEMI). Other controversial issues concern the diagnostic accuracy and cost-effectiveness of cut-off values for the most rapid algorithms (0 h/1 h or 0 h/2 h) to rule-in and rule-out NSTEMI. Finally, another important point is the possible differences between demographic and clinical characteristics of patients enrolled in multicenter trials compared to those routinely admitted to the Emergency Department in Italy. The Study Group of Cardiac Biomarkers, supported by the Italian Scientific Societies Società Italiana di Biochimica Clinica, Italian Society of the European Ligand Assay Society, and Società Italiana di Patolgia Clinica e Medicina di Laboratorio decided to revise the document previously published in 2013 about the management of patients with suspected NSTEMI, and to provide some suggestions for the use of these biomarkers in clinical practice, with a particular focus on the Italian setting.

Relationship between high-sensitivity cardiac troponin T, B-type natriuretic peptide, and physical function in patients with heart failure

AIMS

High-sensitivity cardiac troponin T (hs-cTnT) and B-type natriuretic peptide (BNP) are associated with prognosis and severity in patients with heart failure (HF); however, their association with physical function is unclear. This study aimed to investigate whether hs-cTnT and BNP levels are associated with physical function in patients with HF.

METHODS AND RESULTS

Hs-cTnT, BNP, and physical function (maximal quadriceps isometric strength [QIS], usual gait speed, and 6-min walk distance [6MWD]) were evaluated in 363 consecutive patients with HF (median age, 70 [60-78] years). Patients were divided into four groups according to their median hs-cTnT and BNP levels. After adjusting for demographic characteristics, laboratory levels, and HF severity, higher hs-cTnT and BNP levels were significantly associated with lower physical function (log hs-cTnT, β = -0.162, P = 0.001, for maximal QIS; β = -0.175, P = 0.002, for usual gait speed, and β = -0.129, P = 0.004, for 6MWD; log BNP, β = -0.090, P = 0.092, for maximal QIS, β = 0.038, P = 0.516, for usual gait speed, and β = -0.108, P = 0.023, for 6MWD). In addition, the high hs-cTnT and high BNP group had significantly lower physical function (all P < 0.05) than the low hs-cTnT and low BNP group.

CONCLUSIONS

Higher hs-cTnT and BNP levels are both associated with lower physical function in patients with HF, but hs-cTnT levels showed a more consistent association. The combination of hs-cTnT and BNP may be effective for the stratification of physical function in patients with HF.

Incidence and outcomes of perioperative myocardial infarction/injury diagnosed by high-sensitivity cardiac troponin I

BACKGROUND

 Perioperative myocardial infarction/injury (PMI) diagnosed by high-sensitivity troponin (hs-cTn) T is frequent and a prognostically important complication of non-cardiac surgery. We aimed to evaluate the incidence and outcome of PMI diagnosed using hs-cTnI, and compare it to PMI diagnosed using hs-cTnT.

METHODS

We prospectively included 2455 patients at high cardiovascular risk undergoing 3111 non-cardiac surgeries, for whom hs-cTnI and hs-cTnT concentrations were measured before surgery and on postoperative days 1 and 2. PMI was defined as a composite of perioperative myocardial infarction (PMIInfarct) and perioperative myocardial injury (PMIInjury), according to the Fourth Universal Definition of Myocardial Infarction. All-cause mortality was the primary endpoint.

RESULTS

Using hs-cTnI, the incidence of overall PMI was 9% (95% confidence interval [CI] 8-10%), including PMIInfarct 2.6% (95% CI 2.0-3.2) and PMIInjury 6.1% (95% CI 5.3-6.9%), which was lower versus using hs-cTnT: overall PMI 15% (95% CI 14-16%), PMIInfarct 3.7% (95% CI 3.0-4.4) and PMIInjury 11.3% (95% CI 10.2-12.4%). All-cause mortality occurred in 52 (2%) patients within 30 days and 217 (9%) within 1 year. Using hs-cTnI, both PMIInfarct and PMIInjury were independent predictors of 30-day all-cause mortality (adjusted hazard ratio [aHR] 2.5 [95% CI 1.1-6.0], and aHR 2.8 [95% CI 1.4-5.5], respectively) and, 1-year all-cause mortality (aHR 2.0 [95% CI 1.2-3.3], and aHR 1.8 [95% CI 1.2-2.7], respectively). Overall, the prognostic impact of PMI diagnosed by hs-cTnI was comparable to the prognostic impact of PMI using hs-cTnT.

CONCLUSIONS

Using hs-cTnI, PMI is less common versus using hs-cTnT. Using hs-cTnI, both PMIInfarct and PMIInjury remain independent predictors of 30-day and 1-year mortality.

Laboratory-related issues in the measurement of cardiac troponins with highly sensitive assays

A number of assay-related issues can affect the performance of cardiac troponin (cTn) measurement in everyday practice. In this respect, it is vital that all information on cTn assays is known and that the performance characteristics of assays are objectively assessed and adequately described. The advent of the latest generation of more sensitive cTn assays has heralded a new wave of information about low concentrations of cTn in blood. These recent generation assays have improved analytical sensitivity and corresponding performance at low cTn concentrations when compared to their predecessors, providing a convincing goal for laboratory medicine in helping clinicians in the diagnosis of acute myocardial infarction. Crucial to the clinical utility of highly sensitive cTn assays is the laboratorians' role in closely scrutinizing proposed assays and defining their value in relation to available evidence. Analytical, as well as pre-analytical and post-analytical, aspects must be documented. In this review, we describe what laboratory professionals should know about their cTn assay performance characteristics and the pre-analytical prerequisites for robustness to ensure optimal post-analytical reporting.

Persistent Troponin Elevation in the Setting of an Elevated Rheumatoid Factor: When It Pays to Double Check

A 78-year-old woman presented twice with high sensitivity troponin I (hs-TnI) elevation. Two cardiac catheterizations showed nonocclusive coronary artery disease, and 2 cardiac magnetic resonance imaging scans were normal. With these investigations unable to explain the troponin I (hs-TnI) elevation, alternate troponin samples were sent to check for assay interference. Results from these troponin assays were low. With the patient having elevated rheumatoid factor as a potential contributor to assay interference, the lab reanalyzed the samples using heterophile antibody blocking tubes, revealing lower hs-TnI levels. This case serves as a reminder to consider assay interference when the clinical picture is inconsistent with ischemia.

The role of antibody-based troponin detection in cardiovascular disease: A critical assessment

Cardiovascular disease has remained the world's biggest killer for 30 years. To aid in the diagnosis and prognosis of patients suffering cardiovascular-related disease accurate detection methods are essential. For over 20 years, the cardiac-specific troponins, I (cTnI) and T (cTnT), have acted as sensitive and specific biomarkers to assist in the diagnosis of various types of heart diseases. Various cardiovascular complications were commonly detected in patients with COVID-19, where cTn elevation is detectable, which suggested potential great prognostic value of cTn in COVID-19-infected patients. Detection of these biomarkers circulating in the bloodstream is generally facilitated by immunoassays employing cTnI- and/or cTnT-specific antibodies. While several anti-troponin assays are commercially available, there are still obstacles to overcome to achieve optimal troponin detection. Such obstacles include the proteolytic degradation of N and C terminals on cTnI, epitope occlusion of troponin binding-sites by the cTnI/cTnT complex, cross reactivity of antibodies with skeletal troponins or assay interference caused by human anti-species antibodies. Therefore, further research into multi-antibody based platforms, multi-epitope targeting and rigorous validation of immunoassays is required to ensure accurate measurements. Moreover, with combination and modification of various latest technical (e.g. microfluidics), antibody-based troponin detection systems can be more specific, sensitive and rapid which could be incorporated into portable biosensor systems to be used at point-of care.

Inconsistent Findings of Cardiac Troponin T and I in Clinical Routine Diagnostics: Factors of Influence

Cardiac troponins are crucial for the diagnosis of acute myocardial infarction. Despite known differences in their diagnostic implication, there are no recommendations for only one of the two troponins, cardiac troponin I (cTnI) and troponin T (cTnT) so far. In an everyday routine diagnostic, cTnT (Roche) as well as cTnI (Abbott) were measured in 5667 samples from 3264 patient cases. We investigated the number of identical or discrepant troponin findings. Regarding cTnI, we considered both, sex-dependent and unisex cutoffs. In particular, the number of cTnT positive and cTnI negative results was strikingly high in 14.0% of cTnT positive samples and increases to 23.8% by using sex-specific cTnI cutoffs. This group was considerably greater than the group of cTnI positive and cTnT negative results, also after elimination of patients with an eGFR < 60 mL/min/1.73 m². Comparing the troponin cases with a dynamic increase or decrease between two measurements, we saw a balanced number of discrepant cases (between cTnT+/cTnI- and cTnT-/cTnI+), which was, however, still present. Using ROC analysis, sex-dependent cutoffs improved sensitivity and specificity of cTnI. This study shows in a large cohort that comparing the two cardiac troponins does not amount to identical analytical results. Consideration of sex-dependent cutoffs may improve sensitivity and specificity.

Diagnostic algorithms for non-ST-segment elevation myocardial infarction: open issues

The use of serial measurement of cardiac troponin (cTn) is recommended by international guidelines for the diagnosis of myocardial infarction (MI) since 2000. This article focuses on factors influencing temporal changes in high-sensitive cTn (hs)-cTn and the impact of these factors on the diagnosis of non-ST-segment elevation MI (NSTEMI). The recommendations proposed by three different international guidelines published in 2020-2021 for the management of acute coronary syndromes (ACS) in patients presenting without persistent ST-segment elevation (NSTE) show some discrepancies. In particular, there is no agreement among these guidelines about cut-off or absolute change values to be used for the rule-in, especially regarding the use of sex-specific cut-off values. Furthermore, there are no sufficient evidences on the diagnostic accuracy and cost effectiveness related to cut-off values suggested for algorithms to be used by some hs-cTnI methods.

A colossal, enigmatic, and long-lasting high-sensitivity cardiac troponin T elevation

This case describes the incidental finding of a massive and persistent elevation of troponin T in a patient with end-stage renal disease. This high troponin T value was not consistent with the patient's clinical condition and the laboratory was called in to investigate this discrepancy. After exclusion of analytical interference and discovery of a discordance between troponin T and troponin I, a clinical investigation including cardiac and whole-body magnetic resonance imaging was performed. Magnetic resonance imaging results allowed us to exclude a cardiac origin of troponin elevation but revealed a skeletal muscle pathology. This case constitutes the first description of high-sensitivity cardiac troponin T elevation due to musculoskeletal pathology without cardiac involvement in a patient with end-stage renal disease.

Patients discharged with elevated baseline high-sensitive cardiac troponin T from the emergency department

BACKGROUND

Elevated levels of high-sensitive cardiac troponin T (hs-cTnT) are linked to poor prognosis among emergency department (ED) patients.

OBJECTIVE

Examine the effect of our ED risk assessment among patients with suspected acute coronary syndrome (ACS) and elevated baseline hs-cTnT levels.

DESIGN

Observational cohort study of 16776 ED patients with chest pain or dyspnoea and a hs-cTnT sample analyzed at the time of the ED visit. Of these 1480 patients were sent home with elevated hs-cTnT levels (>14 ng/L).

METHODS

Analysis of clinical and laboratory data from the local hospital and data from the National Board of Health and Welfare.

RESULTS

Admitted patients had 11% and discharged patients had 1.2% 90-day mortality indicating effective risk assessment of patients with suspected ACS. However, if the suspected ACS patient presented with hs-cTnT between 14 and 22 ng/L, the 90-day mortality was 4.1% among discharged and 6.7% among admitted patients. Among discharged patients, an hs-cTnT level above 14 ng/L was a higher independent risk factor for 90-day mortality (HR 3.3, 95% CI 2.9-3.7, p < 0.001) than if the patient was triaged as a high-risk patient (HR 1.6, 95% CI 1.1-1.8, p < 0.001).

CONCLUSIONS

Our ED risk assessment was less effective among patients presenting with elevated hs-cTnT levels.

99th Percentile Upper-Reference Limit of Cardiac Troponin and the Diagnosis of Acute Myocardial Infarction

BACKGROUND

Concerns exist regarding how the 99th percentile upper reference limit (URL) of cardiac troponin (cTn) is determined and whether it should be derived from normal healthy individuals.

CONTENT

The 99th percentile URL of cTn is an important criterion to standardize the diagnosis of myocardial infarction (MI) for clinical, research, and regulatory purposes. Statistical heterogeneity in its calculation exists but recommendations have been proposed. Some negativity has resulted from the fact that with some high-sensitivity (hs) cTn assays, a greater number of increases above the 99th percentile are observed when transitioning from a contemporary assay. Increases reflect acute or chronic myocardial injury and provide valuable diagnostic and prognostic information. The etiology of increases can sometimes be difficult to determine, making a specific treatment approach challenging. For those reasons, some advocate higher cutoff concentrations. This approach can contribute to missed diagnoses. Contrary to claims, neither clinical or laboratory guidelines have shifted away from the 99th percentile. To support the diagnosis of acute MI, the 99th percentile URL remains the best-established approach given the absence of cTn assay standardization. Importantly, risk stratification algorithms using hs-cTn assays predict the possibility of MI diagnoses established using the 99th percentile.

SUMMARY

The 99th percentile of cTn remains the best-established criterion for the diagnosis of acute MI. While not perfect, it is analytically and clinically evidence-based. Until there are robust data to suggest some other approach, staying with the 99th percentile, a threshold that has served the field well for the past 20 years, appears prudent.

Heterophile antibodies, false-positive troponin, and acute coronary syndrome: a case report indicating a pitfall in clinical practice

BACKGROUND

Heterophile antibodies are one of the most common causes of false-positive troponin.

CASE SUMMARY

We report a case of a 53-year-old woman with false-positive troponin elevation and a clinical presentation understood and treated as non-ST-elevation acute coronary syndrome. Because of chronic basal elevation of troponin (at a 'plateau' level) and chest pain, the patient underwent several invasive coronary angiograms until false-positive increase of troponin due to heterophile antibodies was suspected. Borderline stenosis of a left circumflex coronary artery found on first coronary angiogram was a coincidental finding and heterophile antibodies in the patient's serum were confirmed.

DISCUSSION

This interesting case report aims to remind the clinicians about the possibility of false-positive troponin level due to laboratory analytical interference caused by heterophile antibodies. In this case, it is important to suspect false-positive troponin elevation, even when coronary artery disease is found. This rare and less mentioned and/or recognized cause of troponin elevation may lead to unnecessary invasive diagnostics and aggressive treatment of patients.

Cardiac troponins: are there any differences between T and I?

The most recent international guidelines recommend the measurement of cardiac troponin I (cTnI) and cardiac troponin T (cTnT) using high-sensitivity methods (hs-cTn) for the detection of myocardial injury and the differential diagnosis of acute coronary syndromes. Myocardial injury is a prerequisite for the diagnosis of acute myocardial infarction, but also a distinct entity. The 2018 Fourth Universal Definition of Myocardial Infarction states that myocardial injury is detected when at least one value above the 99th percentile upper reference limit is measured in a patient with high-sensitivity methods for cTnI or cTnT. Not infrequently, increased hs-cTnT levels are reported in patients with congenital or chronic neuromuscular diseases, while the hs-cTnI values are often in the normal range. Furthermore, some discrepancies between the results of laboratory tests for the two troponins are occasionally found in individuals apparently free of cardiac diseases, and also in patients with cardiac diseases. In this review article, authors discuss the biochemical, pathophysiological and analytical mechanisms which may cause discrepancies between hs-cTnI and hs-cTnT test results.

The role of coronary computed tomography angiography in evaluation of high troponin patients with narrow-complex supraventricular tachycardia

Aim:

The aim of this study was to investigate the relation of high-sensitive cardiac troponin T (hs-cTnT) elevation with characteristics of supraventricular tachycardia (SVT) episode (duration and maximum heart rate) and coronary computed tomography angiography (CCTA) findings in patients with SVT who presented to the emergency room with palpitation.

Methods:

This retrospective, single-center, noninvasive study included all patients aged between 18 years and 65 years who presented to the emergency department due to narrow-complex SVT and underwent CCTA to rule out coronary artery disease (CAD) due to elevation of hs-cTnT and reverted back to sinus rhythm after intravenous adenosine. The first, second, and the maximum hs-cTnT levels were obtained from the database. The patients were classified into normal coronaries, nonobstructive CAD, and obstructive CAD according to findings of the CCTA. The findings of the groups were compared.

Results:

Eighty-five patients were enrolled in the study. Of them, 21 (26%) patients were female. Sixty-three patients (74%) had normal coronary arteries as per CCTA results, whereas 22 patients (22%) had nonobstructive CAD and two patients (2%) had obstructive CAD. The groups did not differ statistically in respect to hs-cTnT measurements, duration of the arrhythmia, and maximum heart rate at SVT episode. There was no significant statistical correlation between hs-cTnT and the study parameters except the maximum heart rate.

Conclusion:

Cardiac troponins may increase in patients with paroxysmal SVT irrespective of the presence of coronary lesions, and the CCTA may not be an appropriate investigation in the differential diagnosis of paroxysmal SVT with elevated hs-cTnT.

Diagnostic Reclassification by a High-Sensitivity Cardiac Troponin Assay

STUDY OBJECTIVE

Our objective is to describe the rates of diagnostic reclassification between conventional cardiac troponin I (cTnI) and high-sensitivity cardiac troponin T (hs-cTnT) and between combined and sex-specific hs-cTnT thresholds in adult emergency department (ED) patients in the United States.

METHODS

We conducted a prospective, single-center, before-and-after, observational study of ED patients aged 18 years or older undergoing single or serial cardiac troponin testing in the ED for any reason before and after hs-cTnT implementation. Conventional cTnI and hs-cTnT results were obtained from a laboratory quality assurance database. Combined and sex-specific thresholds were the published 99th percentile upper reference limits for each assay. Cases underwent physician adjudication using the Fourth Universal Definition of Myocardial Infarction. Diagnostic reclassification occurred when a patient received a diagnosis of myocardial infarction or myocardial injury with one assay but not the other assay. Our primary outcome was diagnostic reclassification between the conventional cTnI and hs-cTnT assays. Diagnostic reclassification probabilities were assessed with sample proportions and 95% confidence intervals for binomial data.

RESULTS

We studied 1,016 patients (506 men [50%]; median age 60 years [25th, 75th percentiles 49, 71]). Between the conventional cTnI and hs-cTnT assays, 6 patients (0.6%; 95% confidence interval 0.2% to 1.3%) underwent diagnostic reclassification regarding myocardial infarction (5/6 reclassified as no myocardial infarction) and 166 patients (16%; 95% confidence interval 14% to 19%) underwent diagnostic reclassification regarding myocardial injury (154/166 reclassified as having myocardial injury) by hs-cTnT.

CONCLUSION

Compared with conventional cTnI, the hs-cTnT assay resulted in no clinically relevant change in myocardial infarction diagnoses but substantially more myocardial injury diagnoses.

Determination of high sensitive cardiac troponin I 99th percentile upper reference limits in a healthy Pakistani population

OBJECTIVE

This study aims to establish the 99^th percentile upper reference limits of high sensitive cardiac troponin I in a healthy Pakistani population.

METHODS

It was an Observational cohort study carried out in Department of Chemical Pathology and Endocrinology Rehman Medical Institute Peshawar, over the period of one year (January 2019- December 2019). Total 299 cardio-healthy males and females were interviewed and taken past medical history. Based on history, clinical examination, echocardiogram and laboratory data including results of estimated glomerular filtration rate (eGFR) and N-terminal pro-B-type natriureteric peptide (NT-proBNP), subjects with possible subclinical diseases were excluded. High Sensitive Cardiac Troponin I (hs-cTtrop I) was analysed on Abbot ARCHITECT STAT ci8200 using chemiluminescent immunoassay technique. The 99th percentile upper reference limit (URL) of hs-cTtrop I was determined using a non-parametric statistic, while gender specific results were compared.

RESULTS

In this study, 178 males (59.5%) and 121 females (40.5%) were included. The median Interquartile ranges (IQR) of age was 57 (11.6) for males and 56 (13) for females. The 99th percentile URL hs-cTtrop I was found to be 33.9 ng/L, while gender specific values were 38.41ng/L and 15.73ng/L for males and females, respectively (p= 0.0045).

CONCLUSION

High sensitivity cardiac troponin I 99th percentile URL in our study population was found to be 33.9 ng/L with gender specific values being 38.41 ng/L and 15.73ng/L for males and females respectively. Troponin I in males was substantially high in comparison with females.

Fifth generation troponin T assay is subject to antibody interference

BACKGROUND

The fifth generation (high-sensitivity) troponin T assay offers increased precision and analytical sensitivity to the predecessor method. The assay has proven utility in risk stratification and patient management. Upon clinical suspicion and discordant 4th generation troponin T and troponin I results, we investigated a sample for suspected interfering substances to the 5th generation troponin T assay.

METHODS

The analysis included a serial dilution, treatment with polyethylene glycol, commercial antibody blocking reagents, and size exclusion chromatography.

RESULTS

The sample diluted linearly (R² = 0.9957); however, experienced a dramatic reduction in concentration after both the polyethylene glycol and blocking agent treatment. Finally, size exclusion chromatography demonstrated assay reactivity around 970 kDa range.

CONCLUSIONS

These experiments elucidate a heterophilic antibody interference to the assay, and demonstrate potential measures to discern the interference.

Application of the fourth universal definition of myocardial infarction in clinical practice

Purpose: The Fourth Universal Definition of Myocardial Infarction (MI) has highlighted the different pathophysiological mechanisms that may lead to ischaemic and non-ischaemic myocardial injury and has emphasised that the diagnosis of myocardial infarction requires the presence of acute myocardial ischaemia in the setting of acute myocardial injury. This case based review intends to illustrate basic principles on how to apply this new, revised definition in clinical practice.Methods and Results: The distinction between different types of MIs (type 1 or type 2) and the delineation of MI from acute non-ischaemic myocardial injury may be challenging in individual patients, which is illustrated by presenting and discussing real-life routine cases.Conclusions: Type 1 MI is a consequence of coronary plaque rupture or erosion with intracoronary thrombus formation that is usually apparent on coronary angiography. Plausible triggering mechanisms causing myocardial oxygen supply/demand mismatch must be identified for the diagnosis of type 2 MI and its treatment should focus initially on management of the underlying disease attributable to acute myocardial ischaemia.

Spuriously Elevated Cardiac Troponin in the Setting of Atypical Chest Pain Presentation

A 47-year-old woman presented with atypical chest pain and a troponin level of 30.15 ng/dl. A detailed diagnostic work-up did not detect an acute myocardial infarction but revealed the presence of heterophile antibodies. Laboratory values need to be interpreted in the context of the clinical picture when test results do not correspond to clinical findings. (Level of Difficulty: Beginner.)

Circulating Heterophile Antibodies Causing Cardiac Troponin Elevation: An Unusual Differential Diagnosis of Myocardial Disease

We present the case of a female patient who developed persistently elevated levels of cardiac troponin (cTn) after a previous episode of clinically presumed myocarditis. Extensive investigation concluded that the presence of heterophile antibodies was causing false positive cTn elevation. (Level of Difficulty: Intermediate.).

Diagnosis and risk stratification of chest pain patients in the emergency department: focus on acute coronary syndromes. A position paper of the Acute Cardiovascular Care Association

This paper provides an update on the European Society of Cardiology task force report on the management of chest pain. Its main purpose is to provide an update on the decision algorithms and diagnostic pathways to be used in the emergency department for the assessment and triage of patients with chest pain symptoms suggestive of acute coronary syndromes.

Acute versus chronic myocardial injury and long-term outcomes

OBJECTIVE

There is a paucity of data regarding prognosis in patients with acute versus chronic myocardial injury for long-term outcomes. We hypothesised that patients with chronic myocardial injury have a similar long-term prognosis as patients with acute myocardial injury.

METHODS

In an observational cohort study of 22 589 patients who had high-sensitivity cardiac troponin T (hs-cTnT) measured in the emergency department during 2011-2014, we identified all patients with level >14 ng/L and categorised them as acute myocardial injury, type 1 myocardial infarction (T1MI), type 2 myocardial infarction (T2MI) or chronic myocardial injury through adjudication. We estimated adjusted HRs with 95% CIs for the primary outcome all-cause mortality and secondary outcomes MI, and heart failure in patients with acute myocardial injury, T1MI and T2MI compared with chronic myocardial injury.

RESULTS

In total, 3853 patients were included. During 3.9 (±2) years of follow-up, 48%, 24%, 44% and 49% of patients with acute myocardial injury, T1MI, T2MI and chronic myocardial injury died, respectively. Patients with acute myocardial injury had higher adjusted risks of death (1.21, 95% CI 1.08 to 1.36) and heart failure (1.24, 95% CI 1.07 to 1.43), but a similar risk for myocardial infarction (MI) compared with the reference group. Patients with T1MI had a lower adjusted risk of death (0.86, 95% CI 0.74 to 1.00) and higher risk of MI (2.09, 95% CI 1.62 to 2.68), but a similar risk of heart failure. Patients with T2MI had a higher adjusted risk of death (1.46, 95% CI 1.18 to 1.80) and heart failure (1.30, 95% CI 1.00 to 1.69) compared with patients with chronic myocardial injury.

CONCLUSIONS

Absolute long-term risks for death are similar, and adjusted risks are slightly higher, among patients with acute myocardial injury and T2MI, respectively, compared with chronic myocardial injury. The lowest risk of long-term mortality was found in patients with T1MI. Both acute and chronic myocardial injury are associated with very high risks of adverse outcomes.

High-sensitivity troponin assays: development and utility in a modern health-care system

Introduction: The introduction of cardiac troponin (cTn) assays have revolutionized the diagnosis and management of acute myocardial infarction in Emergency Departments worldwide. Its success has led to significant research and development investment in this area culminating in the development of newer high-sensitivity cardiac troponin assays (hs-cTn). While these newer assays allow for more rapid diagnosis by decreasing the time interval between serial data points, there is an inevitable trade off between increasing sensitivity and specificity. This review examines in detail the introduction and implementation of hs-cTN and its implications for clinical practice.Areas covered: This article reviews the history and development of high-sensitivity troponin assays and their application to clinical practice and current evidence base. It also discusses both the positive and negative aspects of the continuing increasing sensitivity of biochemical assays and the translation of this into clinical practice. Potential future developments are also discussed.Expert commentary: It is clear that there are many benefits to detecting extremely low concentration of cardiac troponin including the development of rapid rule out algorithms and the cost and time-saving advantages associated with the quicker movement of patients through the health-care system. It is important to note however that detecting troponin at very low concentrations also dramatically increases the false-positive rates and leads to a potentially large increase in invasive testing and diagnosis of myocardial infarction.

Evaluation of Molecularly Imprinted Polymers for Point-of-Care Testing for Cardiovascular Disease

Molecular imprinting is a rapidly growing area of interest involving the synthesis of artificial recognition elements that enable the separation of analyte from a sample matrix and its determination. Traditionally, this approach can be successfully applied to small analyte (<1.5 kDa) separation/ extraction, but, more recently it is finding utility in biomimetic sensors. These sensors consist of a recognition element and a transducer similar to their biosensor counterparts, however, the fundamental distinction is that biomimetic sensors employ an artificial recognition element. Molecularly imprinted polymers (MIPs) employed as the recognition elements in biomimetic sensors contain binding sites complementary in shape and functionality to their target analyte. Despite the growing interest in molecularly imprinting techniques, the commercial adoption of this technology is yet to be widely realised for blood sample analysis. This review aims to assess the applicability of this technology for the point-of-care testing (POCT) of cardiovascular disease-related biomarkers. More specifically, molecular imprinting is critically evaluated with respect to the detection of cardiac biomarkers indicative of acute coronary syndrome (ACS), such as the cardiac troponins (cTns). The challenges associated with the synthesis of MIPs for protein detection are outlined, in addition to enhancement techniques that ultimately improve the analytical performance of biomimetic sensors. The mechanism of detection employed to convert the analyte concentration into a measurable signal in biomimetic sensors will be discussed. Furthermore, the analytical performance of these sensors will be compared with biosensors and their potential implementation within clinical settings will be considered. In addition, the most suitable application of these sensors for cardiovascular assessment will be presented.

Multi-Site Coronary Vein Sampling Study on Cardiac Troponin T Degradation in Non-ST-Segment-Elevation Myocardial Infarction: Toward a More Specific Cardiac Troponin T Assay

Background Cardiac troponin T ( cTnT ) is seen in many other conditions besides myocardial infarction, and recent studies demonstrated distinct forms of cTnT . At present, the in vivo formation of these different cTnT forms is incompletely understood. We therefore performed a study on the composition of cTnT during the course of myocardial infarction, including coronary venous system sampling, close to its site of release. Methods and Results Baseline samples were obtained from multiple coronary venous system locations, and a peripheral artery and vein in 71 non- ST -segment-elevation myocardial infarction patients. Additionally, peripheral blood was drawn at 6- and 12-hours postcatheterization. cTnT concentrations were measured using the high-sensitivity- cTnT immunoassay. The cTnT composition was determined via gel filtration chromatography and Western blotting in an early and late presenting patient. High-sensitivity - cTnT concentrations were 28% higher in the coronary venous system than peripherally (n=71, P<0.001). Coronary venous system samples demonstrated cT n T-I-C complex, free intact cTnT , and 29 kD a and 15 to 18 kD a cTnT fragments, all in higher concentrations than in simultaneously obtained peripheral samples. While cT n T-I-C complex proportionally decreased, and disappeared over time, 15 to 18 kD a cTnT fragments increased. Moreover, cT n T-I-C complex was more prominent in the early than in the late presenting patient. Conclusions This explorative study in non- ST -segment-elevation myocardial infarction shows that cTnT is released from cardiomyocytes as a combination of cT n T-I-C complex, free intact cTnT , and multiple cTnT fragments indicating intracellular cTnT degradation. Over time, the cT n T-I-C complex disappeared because of in vivo degradation. These insights might serve as a stepping stone toward a high-sensitivity- cTnT immunoassay more specific for myocardial infarction.

Description of interference in the measurement of troponin T by a high-sensitivity method

Introduction

Measurement of high-sensitivity troponin T (hs-TnT) has become an essential step in the diagnosis of acute myocardial infarction. This high-sensitivity method allows quantifying the concentration of troponin T in blood of healthy subjects with a lower inaccuracy compared to previous reagent generations. However, the presence of certain compounds in the sample may interfere with the result. We present a patient who had repeatedly high concentrations of hs-TnT in the serum sample that did not agreed with the signs and symptoms. In addition, ultrasensitive troponin I concentration was undetectable.

Materials and methods

To investigate the presence of an interfering compound, different analysis were carried out. In order to discard macro complexes in the sample, the serum was precipitated with polyethylene glycol. In addition, the serum was incubated with Scantibodies Heterophilic Blocking Tube, which can block heterophilic antibodies. Finally, a size exclusion chromatography of the sample was performed by the manufacturer.

What happened

The interfering substance was allocated into fractions with proteins of 150kDa, corresponding to high molecular weight proteins like immunoglobulin G (IgG). This compound was responsible for the falsely elevated hs-TnT results and it affected only the high-sensitivity methods.

Main lesson

The detected interfering compound was probably an IgG. This type of interference must be kept in mind in front of discordant results, even if they are extremely rare. Therefore, interdisciplinary cooperation between clinicians, laboratory and manufacturer is essential.

False-positive troponin I elevation in a newborn with neonatal encephalopathy

Serum biomarkers of myocardial damage are commonly used in babies after perinatal asphyxia. We present a case report of a persistently troponin I elevation without evidence of clinical or instrumental signs of myocardial ischaemia in a baby with perinatal asphyxia. When the blood was mixed with polyethylene glycol we found that the troponin I levels were falsely elevated due to interfering antibodies. This case shows that analytical errors may still occur despite modern immunoassay systems and underlines the need for further investigations to identify false-positive values in case of disagreement between clinical conditions and laboratory values.