Improved troponin T ELISA specific for cardiac troponin T isoform: assay development and analytical and clinical validation

Abstract The first generation of troponin T ELISA (TnT 1) can yield false-positive results in patients with severe skeletal muscle injury. Therefore, a cardiac-specific second-generation troponin T ELISA (TnT 2) was developed, in which the cross-reactive antibody 1B10 has been replaced by a high-affinity cardiac-specific antibody M11.7. No cross-reactivity of TnT 2 was observed with purified skeletal muscle troponin T (1000 μg/L) or in test samples from 43 marathon runners and 24 patients with rhabdomyolysis and highly increased creatine kinase. TnT 2 was increased >0.2 μg/L in 5 of 40 patients with renal failure and in 4 of 20 muscular dystrophy patients. The detection limit is 0.012 μg/L. Day-to-day imprecision (CV) within the range 0.19–14.89 μg/L was <5.8%. In 4955 patients without myocardial damage, 99.6% had TnT <0.10 μg/L. Assay comparison (TnT 1 vs TnT 2) over the whole concentration range (i.e., in 323 samples from AMI-suspected patients) showed a slope, intercept, and standard error of estimate (Sey) of 1.18, 0.01 μg/L, and 0.81 μg/L, respectively.

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Multicenter evaluation of a second-generation assay for cardiac troponin T

Clinical Chemistry ◽

10.1093/clinchem/43.10.1877 ◽

1997 ◽

Vol 43 (10) ◽

pp. 1877-1884 ◽

Cited By ~ 62

Author(s):

Hannsjörg Baum ◽

Siegmund Braun ◽

Willie Gerhardt ◽

Georges Gilson ◽

Gerd Hafner ◽

...

Keyword(s):

Skeletal Muscle ◽

Cardiac Troponin ◽

First Generation ◽

Second Generation ◽

Troponin T ◽

Myocardial Damage ◽

Cross Reactivity ◽

Cardiac Troponin T ◽

Marathon Runners ◽

Assay Time

Abstract We report on the evaluation of the second-generation assay for cardiac troponin T (cTnT) on the Enzymun®system. This new assay is completely specific for the cardiac isoform of TnT, utilizing two cardiospecific monoclonal antibodies. The assay time is reduced to 45 min. The interassay precision shows a median CV of 5.5%; 20% interassay CV was found between 0.05 and 0.1 μg/L. The cardiosensitivity of the second-generation cTnT assay in patients with ischemic myocardial injury appears equivalent when compared with the first-generation assay. We found no falsely positive results in patients with skeletal muscle damage including multitraumas, surgery patients, and marathon runners who showed highly increased values with the unspecific first-generation assay. In Duchenne disease cTnT was still increased, but to a much lower extent. cTnT remains increased in renal failure, but to a lesser degree than with the first-generation assay. The cause of this increase remains unclear. Although a cross-reactivity of skeletal muscle TnT in the second-generation assay could be excluded by our findings, minor myocardial damage or expression of the cardiac isoform of TnT in regenerating muscles cannot be ruled out in those cases with apparently falsely increased cTnT values. The second-generation cTnT assay is a step forward in the combination of cardiosensitivity and cardiospecificity in biochemical markers for diagnosis of heart disease.

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Cardiac troponin I, cardiac troponin T, and creatine kinase MB in dialysis patients without ischemic heart disease: evidence of cardiac troponin T expression in skeletal muscle

Clinical Chemistry ◽

10.1093/clinchem/43.6.976 ◽

1997 ◽

Vol 43 (6) ◽

pp. 976-982 ◽

Cited By ~ 133

Author(s):

Mary D McLaurin ◽

Fred S Apple ◽

Ellen M Voss ◽

Charles A Herzog ◽

Scott W Sharkey

Keyword(s):

Skeletal Muscle ◽

Heart Disease ◽

Ischemic Heart Disease ◽

Cardiac Troponin ◽

First Generation ◽

Troponin T ◽

Ischemic Heart ◽

Cardiac Troponin T ◽

Dialysis Patients ◽

Acute Ischemic Heart Disease

Abstract Serum cardiac troponin T (cTnT) concentrations are frequently increased in chronic dialysis patients as measured by the first-generation ELISA immunoassay, as is creatine kinase (CK) MB mass in the absence of acute ischemic heart disease. We designed this study to compare four serum markers of myocardial injury [CK-MB mass, first-generation ELISA cTnT, second-generation Enzymun cTnT, and cardiac troponin I (cTnI)] in dialysis patients without acute ischemic heart disease. We also evaluated skeletal muscle from dialysis patients as a potential source of serum cTnT. No patients in the clinical evaluation group (n = 24) studied by history and by physical examination, electrocardiography, and two-dimensional echocardiography had evidence of ischemic heart disease. Biochemical markers were measured in serial predialysis blood samples with specific monoclonal antibody-based immunoassays. For several patients at least one sample measured above the upper reference limit: CK-MB, 7 of 24 (30%); ELISA cTnT, 17 of 24 (71%); Enzymun cTnT, 3 of 18 (17%); and cTnI, 1 of 24 (4%). In a separate group of dialysis patients (n = 5), expression of cTnT, but not cTnI, was demonstrated by Western blot analysis in 4 of 5 skeletal muscle biopsies. Chronic dialysis patients without acute ischemic heart disease frequently had increased serum CK-MB and cTnT. The specificity of the second-generation cTnT (Enzymun) assay was improved over that of the first-generation (ELISA) assay; cTnI was the most specific of the currently available biochemical markers. cTnT, but not cTnI, was expressed in the skeletal muscle of dialysis patients.

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P4420Is exercise-induced cardiac troponin release caused by skeletal muscle injury?

European Heart Journal ◽

10.1093/eurheartj/ehz745.0822 ◽

2019 ◽

Vol 40 (Supplement_1) ◽

Author(s):

T Paana ◽

S Jaakkola ◽

E Tuunainen ◽

S Wittfooth ◽

K Bamberg ◽

...

Keyword(s):

Skeletal Muscle ◽

Cardiac Troponin ◽

Muscle Injury ◽

Troponin I ◽

Troponin T ◽

Skeletal Muscle Injury ◽

Coronary Syndrome ◽

Marathon Race ◽

Recreational Runners ◽

Exercise Induced

Abstract Background Cardiac troponins (cTn) are highly sensitive and specific markers for cardiac injury and a key element in the diagnosis of acute coronary syndrome. Strenuous exercise is known to induce increases in cTn, but the causative factors remain ambiguous. It is also equivocal whether exercise induced skeletal muscle injury is associated with cTn elevation. Purpose The aim of this study was to identify independent predictors for the rise in cardiac troponin T (cTnT) and I (cTnI) concentration and to focus on the relationship between skeletal muscle injury measured by skeletal troponin I (skTnI) and cTn elevations after a marathon race in a large group of male recreational runners. Methods A total of 40 recreational runners participating in the marathon in our city were recruited. The study included baseline visit (prerace) and immediate post-race sampling. Results The post-marathon cTnT concentration rose above the reference limit in 38 (95%) participants and the detection limit for cTnI was exceeded in 34 (85%) participants. Similarly, a 10-fold increase in skTnI concentration was observed and elevated post-race values were seen in all participants. There was no significant correlation between the post-race cTnT or cTnT change and post-race skTnI (Spearman's rho = 0.249, p=0.122, rho = 0.285, p=0.074). However, post-race cTnI and change in cTnI were associated with post-race skTnI (rho = 0.404, p=0.01, rho = 0.460, p=0.003) and creatine kinase (r=0.368, p=0.019) concentration. Subjective exertion or self-reported muscle symptoms did not correlate with post-race cTnT, cTnI or skTnI levels. Post-Race cTnT <40 Post-Race cTnT ≥40 p-value n=18 n=22 Age, years 53.3±12.2 44.0±11.9 0.002 Active training, years 12.0 (9.3) 17.0 (15.8) 0.190 Muscle symptoms 7 (38.9) 11 (52.4) 0.523 Creatinine kinase, ug/l 406 (137) 399 (319) 0.163 N-terminal proBNP ng/l 137±168 158±277 0.783 Skeletal Troponin I, ng/ml 28.6 (41) 56.7 (143) 0.199 Figure 1 Conclusions Cardiac troponin became abnormal in almost all runners after marathon race. The exercise-induced rise in cardiac troponin I is related to simultaneous release of skeletal troponin I. The mechanism of this association remains uncertain, but clinicians should be cautious when interpreting post-exercise troponin levels without clinical symptoms and signs of myocardial ischemia.

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Cardiac Troponin I and T Concentrations in Patients with Cocaine-Associated Chest Pain

Annals of Clinical Biochemistry International Journal of Laboratory Medicine ◽

10.1177/000456329603300301 ◽

1996 ◽

Vol 33 (3) ◽

pp. 183-186 ◽

Cited By ~ 30

Author(s):

Mary McLaurin ◽

Fred S Apple ◽

Timothy D Henry ◽

Scott W Sharkey

Keyword(s):

Skeletal Muscle ◽

Chest Pain ◽

Cardiac Troponin ◽

Muscle Injury ◽

Troponin I ◽

Troponin T ◽

Acute Chest Pain ◽

Cardiac Troponin I ◽

Skeletal Muscle Injury ◽

Rule Out

Patients with cocaine-related chest pain with electrocardiographic (ECG) abnormalities are often admitted to rule out acute myocardial infarction (AMI). Cardiac troponin I and T should be superior to measurement of creatine kinase (CK)—MB for detecting cardiac injury in patients with coexisting skeletal muscle injury. We prospectively evaluated 19 consecutive patients with acute chest pain related to cocaine use who were hospitalized to rule out AMI. The admission ECG was abnormal in 16 of 19 patients. Total CK and CK—MB were elevated during the hospital course in 14 and 3 patients, respectively. Cardiac troponin I and cardiac troponin T levels were within normal limits in all patients demonstrating that recent myocardial injury did not occur. Clinically, no patient had an AMI. Cocaine-induced thoracic skeletal muscle injury or transient cocaine-induced coronary vasospasm should be considered as alternative sources of chest pain in these patients.

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Skeletal myopathies as a non-cardiac cause of elevations of cardiac troponin concentrations

Diagnosis ◽

10.1515/dx-2019-0045 ◽

2019 ◽

Vol 6 (3) ◽

pp. 189-201 ◽

Cited By ~ 1

Author(s):

Evangelos Giannitsis ◽

Christian Mueller ◽

Hugo A. Katus

Keyword(s):

Skeletal Muscle ◽

Cardiac Troponin ◽

Troponin T ◽

Imaging Techniques ◽

Cross Reactivity ◽

Protein Characterization ◽

Lower Sensitivity ◽

Adult Skeletal Muscle ◽

Contrast Enhanced ◽

Magnetic Resonance Imaging Mri

AbstractSkeletal myopathies have been suggested as a non-cardiac cause of elevations of cardiac troponin (cTn), particularly cardiac troponin T (cTnT). This is of major clinical relevance and concern as cTn plays a major role in the early diagnosis of myocardial infarction (MI). While both the incidence as well as the true pathophysiology (cardiac versus non-cardiac) underlying elevations in cTn in skeletal myopathies remain largely unknown, re-expression of cTnT in regenerating adult skeletal muscle has been suggested as a possible contributor. However, unequivocal protein characterization in skeletal muscle and quantification of the relative amounts of this possible signal versus the cTn signal derived from true cardiomyocyte injury remains elusive. Alternatively, minor cross-reactivity of the cTnT (and possibly at times also cTnI) detection and capture antibodies used in current monoclonal immunoassays with the skeletal troponin T or I isoform may be considered. Both would represent “false positive” elevations from a clinical perspective and would need to be reliably differentiated from “true positive elevations” from subclinical cardiomyocyte injury not detectable by currently available imaging techniques such as echocardiography and contrast enhanced magnetic resonance imaging (MRI), which have at least a 5 times lower sensitivity for cardiomyocyte injury. This review aims to explore the currently available data, its methodological limitations and provide guidance to clinicians to avoid misinterpretation of cTn concentrations.

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Analytical validation of a high-sensitivity cardiac troponin T assay in horses

Journal of Veterinary Diagnostic Investigation ◽

10.1177/1040638715593601 ◽

2015 ◽

Vol 27 (4) ◽

pp. 504-509 ◽

Cited By ~ 5

Author(s):

Nicky Van Der Vekens ◽

Marie-Astrid van Dievoet ◽

Hendrik De Puydt ◽

Annelies Decloedt ◽

Sofie Ven ◽

...

Keyword(s):

Cardiac Troponin ◽

Troponin T ◽

Myocardial Damage ◽

High Sensitivity ◽

Cross Reactivity ◽

Cardiac Troponin T ◽

Plasma Samples ◽

Analytical Validation ◽

Serum Samples ◽

Coefficients Of Variation

Although cardiac troponin T (cTnT) assays have been used to detect myocardial damage in horses, a cTnT assay has not been analytically validated, to our knowledge. The aims of this study were to estimate the precision of a high-sensitivity cTnT assay in horses and determine the effect of hemolysis on the measured cTnT concentration. Serum samples from horses were mixed in 3 different pools. Pool 1 consisted of samples from 3 healthy horses, pool 2 from 6 horses with heart failure or atypical myopathy, and pool 3 from 10 horses with atypical myopathy. The within- and between-run coefficients of variation were determined for each pool. Pools 2 and 3 were diluted to estimate linearity. To study the influence of sample hemolysis, serum was collected from 4 horses with a high cTnT concentration, in which hemolysis was mechanically induced. In addition, ethylenediamine tetra-acetic acid blood tubes were collected from 3 other horses, from which hemolysate was prepared and added to plasma at different concentrations. The within- and between-run coefficients of variation of all pools were <10%, and a good linearity was found. Three out of 4 hemolyzed serum samples had a decreased serum cTnT concentration. Plasma samples with a high hemolysis index showed a negative interference, resulting in a lower cTnT concentration. Results of the high-sensitivity cTnT assay were highly reproducible. Because samples from horses with musculoskeletal damage were included, further studies should test the possible cross-reactivity between troponin T of musculoskeletal and cardiac origin before the assay can be used in equine clinical practice.

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