The calculation of the cardiac troponin T 99th percentile of the reference population is affected by age, gender, and population selection: a multicenter study in Italy

Sex-Specific Versus Overall Clinical Decision Limits for Cardiac Troponin I and T for the Diagnosis of Acute Myocardial Infarction: A Systematic Review

BACKGROUND

The overall clinical decision limits of high-sensitivity cardiac troponin I (hs-cTnI; 26 ng/L) and T (hs-cTnT; 14 ng/L) may contribute to underdiagnosis of acute myocardial infarction in women. We performed a systematic review to investigate sex-specific and overall 99th percentiles of hs-cTnI and hs-cTnT derived from healthy reference populations.

CONTENT

We searched in PubMed and EMBASE for original studies, and by screening reference lists. Reference populations designed to establish 99th percentiles of hs-cTnI (Abbott) and/or hs-cTnT (Roche), published between January 2009 and October 2017, were included. Sex-specific and overall 99th percentile values of hs-cTnI and hs-cTnT were compared with overall clinical decision ranges (hs-cTnI, 23-30 ng/L; hs-cTnT, 13-25 ng/L). Twenty-eight studies were included in the systematic review. Of 16 hs-cTnI and 18 hs-cTnT studies, 14 (87.5%) and 11 (61.1%) studies reported lower female-specific hs-cTn cutoffs than overall clinical decision ranges, respectively. Conversely, male-specific thresholds of both hs-cTnI and hs-cTnT were in line with currently used overall thresholds, particularly hs-cTnT (90% concordance). The variation of estimated overall 99th percentiles was much higher for hs-cTnI than hs-cTnT (29.4% vs 80.0% of hs-cTnI and hs-cTnT studies reported values within the current overall clinical decision range, respectively).

SUMMARY

Our data show substantially lower female-specific upper reference limits of hs-cTnI and hs-cTnT than overall clinical decision limits of 26 ng/L and 14 ng/L, respectively. The statistical approach strongly affects the hs-cTnI threshold. Downward adjustment of hs-cTn thresholds in women may be warranted to reduce underdiagnosis of acute myocardial infarction in women.

Evaluation of analytical performance of a new high-sensitivity immunoassay for cardiac troponin I

Background:

The study aim was to evaluate and compare the analytical performance of the new chemiluminescent immunoassay for cardiac troponin I (cTnI), called Access hs-TnI using DxI platform, with those of Access AccuTnI+3 method, and high-sensitivity (hs) cTnI method for ARCHITECT platform.

Methods:

The limits of blank (LoB), detection (LoD) and quantitation (LoQ) at 10% and 20% CV were evaluated according to international standardized protocols. For the evaluation of analytical performance and comparison of cTnI results, both heparinized plasma samples, collected from healthy subjects and patients with cardiac diseases, and quality control samples distributed in external quality assessment programs were used.

Results:

LoB, LoD and LoQ at 20% and 10% CV values of the Access hs-cTnI method were 0.6, 1.3, 2.1 and 5.3 ng/L, respectively. Access hs-cTnI method showed analytical performance significantly better than that of Access AccuTnI+3 method and similar results to those of hs ARCHITECT cTnI method. Moreover, the cTnI concentrations measured with Access hs-cTnI method showed close linear regressions with both Access AccuTnI+3 and ARCHITECT hs-cTnI methods, although there were systematic differences between these methods. There was no difference between cTnI values measured by Access hs-cTnI in heparinized plasma and serum samples, whereas there was a significant difference between cTnI values, respectively measured in EDTA and heparin plasma samples.

Conclusions:

Access hs-cTnI has analytical sensitivity parameters significantly improved compared to Access AccuTnI+3 method and is similar to those of the high-sensitivity method using ARCHITECT platform.

High-sensitivity detection of cardiac troponin I with UV LED excitation for use in point-of-care immunoassay

High-sensitivity cardiac troponin assay development enables determination of biological variation in healthy populations, more accurate interpretation of clinical results and points towards earlier diagnosis and rule-out of acute myocardial infarction. In this paper, we report on preliminary tests of an immunoassay analyzer employing an optimized LED excitation to measure on a standard troponin I and a novel research high-sensitivity troponin I assay. The limit of detection is improved by factor of 5 for standard troponin I and by factor of 3 for a research high-sensitivity troponin I assay, compared to the flash lamp excitation. The obtained limit of detection was 0.22 ng/L measured on plasma with the research high-sensitivity troponin I assay and 1.9 ng/L measured on tris-saline-azide buffer containing bovine serum albumin with the standard troponin I assay. We discuss the optimization of time-resolved detection of lanthanide fluorescence based on the time constants of the system and analyze the background and noise sources in a heterogeneous fluoroimmunoassay. We determine the limiting factors and their impact on the measurement performance. The suggested model can be generally applied to fluoroimmunoassays employing the dry-cup concept.

Evidence of direct cardiac damage following high-intensity exercise in chronic energy restriction: A case report and literature review

RATIONALE

Following prolonged endurance events such as marathons, elevated levels of cardiospecific biomarkers are commonly reported. Although transiently raised levels are generally not considered to indicate clinical myocardial damage, comprehension of this phenomenon remains incomplete. The popularity of high-intensity interval training highlights a paucity of research measuring cardiac biomarker response to this type of exercise. This a posteriori case report discusses the elevation of cardiac troponins (cTn) associated with short interval, high-intensity exercise.

PATIENT CONCERNS

In this case report, an apparently healthy 29-year-old recreationally active female presented clinically raised cardiac troponin I (cTnI) levels (>0.04 ng/mL), after performing high-intensity cycle ergometer sprints. As creatine kinase (CK) is expressed by multiple organs (e.g., skeletal muscle, brain, and myocardium), cTnI assays were performed to determine any changes in total serum CK levels not originating from skeletal muscle damage.

DIAGNOSIS

A posteriori the individual's daily energy expenditure indicated chronically low-energy availability. Psychometric testing suggested that the individual scored positive for disordered eating, highly for fatigue levels, and low in mental health components.

OUTCOMES

The current case report provides novel evidence of elevated cTnI occurring as a result of performing short duration, high intensity, cycle ergometer exercise in an individual with self-reported chronically depleted energy balance. A schematic to identify potentially "at risk" individuals is presented.

LESSONS

Considering this as a case report, results cannot be generalized; however, the main findings suggest that individuals who habitually restrict their calorie intake below their bodies' daily energy requirements, may have elevated biomarkers of exercise induced myocardial stress from performing high-intensity exercise.

Establishment of a reference interval for high-sensitivity cardiac troponin I in healthy adults from the Sichuan area

High-sensitivity cardiac troponin I (hs-cTnI) has been used in the diagnosis and risk stratification of acute myocardial infarction. However, there is no common consensus on an hs-cTnI reference interval for the Chinese population. The aim of this study was to describe the distribution of hs-TnI and establish the 99th percentile reference interval for hs-cTnI in healthy adults from the Sichuan area.Serum specimens were collected from 1485 healthy adults (731 men and 754 women ranging in age from 18 to 85 years) in Sichuan Provincial People's Hospital. All specimens were divided into 4 groups according to age distribution: 18 to 35 years, 36 to 50 years, 51 to 65 years, and ≥66 years. Specimens were further divided into younger/middle and older-aged groups based on a cut-off age of 50 years. The serum hs-cTnI concentration was determined using the Abbott ARCHITECT STAT hs-cTnI assay.The serum hs-cTnI concentration increased with age (P < 0.05). The 99th percentiles of hsTnI were 28.0 pg/mL among the whole population, 31.1 pg/mL among men, and 22.7 pg/mL among women. The age-dependent 99th percentiles of hs-cTnI in men and women were as follows: 28.8 versus 12.5 pg/mL for 18 to 35 years, 20.4 versus 9.2 pg/mL for 36 to 50 years, 24.2 versus 13.6 pg/mL for 51 to 65 years, and 27.9 versus 32.2 pg/mL for ≥66 years.The 99th percentile reference interval for hs-cTnI in healthy adults from the Sichuan area was similar to the manufacturer's recommendation. Men had a higher 99th percentile hs-cTnI value than women in the age range of 18 to 65 years.

The 99th percentile of reference population for cTnI and cTnT assay: methodology, pathophysiology and clinical implications

According to recent international guidelines, including the 2012 Third Universal Definiton of Myocardial Infarction by the Joint ESC/ACCF/AHA/WHF Task Force, an increase in cardiac troponin (cTn) levels over the 99th percentile upper reference limit (99th URL) should be considered clinically relevant, this cut-off being measured with an imprecision ≤10 CV%. In theory 99th URL values strongly depend not only on demographic and physiological variables (i.e. criteria for considering the reference population “healthy”), but also on the analytical performance of cTn methods and mathematical algorithms used for the calculation. The aim of the present article was therefore to review the methodological and pathophysiological factors affecting the evaluation and calculation of the 99th URL for cTn assay. The critical analysis made showed that no uniform procedure is followed, and nor have experts or regulatory bodies provided uniform guidelines for researchers or cTn assays manufacturers as an aid in “their quest to define normality”. In particular, little attention has been paid to the way in which a healthy reference population is to be selected, or the criteria for calculating the 99th URL value for cTn assays, thus highlighting the need for international recommendations not only for demographic and physiological variables criteria for defining a healthy reference population, but also for calculating mathematical algorithms for establishing/calculating clinical decision values. An expert consensus group, comprising laboratory and clinical scientists, biomedical statisticians, industrial and regulatory representatives, should be responsible for drawing up these guidelines.

Advances in Cardiac Biomarkers of Acute Coronary Syndrome

Acute coronary syndrome (ACS) encompasses a pathophysiological spectrum of cardiovascular diseases, all of which have significant morbidity and mortality. ACS was once considered an acute condition; however, new treatment strategies and improvements in biomarker assays have led to ACS being an acute and chronic disease. Cardiac troponin is the preferred biomarker for the diagnosis of myocardial infarction, and there is considerable interest and efforts toward development and implementation of high-sensitivity cardiac troponin (hs-cTn) assays worldwide. Analytical and clinical performance characteristics of hs-cTn assays as well as testing limitations are important for laboratorians and clinicians to understand in order to utilize testing appropriately. Furthermore, expanding the clinical utility of hs-cTn into other cohorts such as asymptomatic community dwelling populations, heart failure, and chronic kidney disease populations supports novel opportunities for improved short- and long-term prognosis.

High-sensitivity cardiac troponin testing in routine practice: economic and organizational advantages

Very seldom, if ever, a single laboratory test has provided such a paradigm shift in the managed care as cardiac troponin (cTn) testing. More than twenty years of improvements in test design and analytical features have contributed to revolutionize the clinical recommendations and guidelines, and the diagnosis of myocardial infarction (MI) is now highly dependent upon the kinetics of cTn within a suggestive clinical setting. Despite the advent of high-sensitivity cTn (HS-cTn) immunoassays has allowed a more accurate and timely diagnosis as well as a higher prognostic accuracy, the focus is now shifting on the most suitable algorithms and on a comprehensive approach to the clinical management of acute coronary syndrome (ACS). In this article we aim to discuss the implications of HS-cTn testing for ruling out and ruling in ACS. In the latter instance, main improvements are related to ACS diagnosis in women, in whom this pathology is still often underdiagnosed or misdiagnosed. A quick and accurate rule out will also regarded as a great advantage from both an organizational and economic standpoint. The advantages that will stem from this new approach have been recently assessed, and shortening of repeated testing 1 or 2 h from conventional algorithms entailing blood sampling at 3 and 6 h seems attainable. The larger benefits will definitely occur in clinical settings where the actual diagnosis rate of MI among patients with suspect ACS is lower and, consequently, the negative predictive value (NPV) of HS-cTn is the highest.

Present and Future of Cardiac Troponin in Clinical Practice: A Paradigm Shift to High-Sensitivity Assays

Despite its wide utilization and central role in the evaluation of patients with potential ischemic symptoms, misconceptions and confusion about cardiac troponin (cTn) prevail. The implementation of high-sensitivity (hs) cTn assays in clinical practice has multiple potential advantages provided there is an education process tied to the introduction of these assays that emphasizes the appropriate utilization of the test. Several diagnostic strategies have been explored with hs-cTn assays, including the use of undetectable values, accelerated serial hs-cTn sampling, hs-cTn measurements in combination with a clinical-risk score, and the use of a single hs-cTn measurement with a concentration threshold tailored to meet a clinical need. In this document we discuss basic concepts that should facilitate the integration of hs-cTn assays into clinical care in years to come.

Reference values of galectin-3 and cardiac troponins derived from a single cohort of healthy blood donors

BACKGROUND

Here we describe the determination of upper reference limits (URL) for galectin-3, high-sensitivity cardiac troponin I (hs-cTnI) and high-sensitivity cardiac troponin T (hs-cTnT) in a single cohort of healthy blood donors using routine assays.

METHODS

For this reference value study, we used a cohort of 402 consecutive blood donors (64% were male and 36% were female). The median individuals' age was 35.0 years (range, 18.0-64.4). Individuals of this reference population were free of cardiovascular disease, diabetes mellitus, renal disease, cancer, current infection and chronic inflammatory disease. Plasma concentrations of galectin-3 were measured with the "routine Galectin-3" assay (Abbott Diagnostics), of hs-cTnI with the "STAT High Sensitive Troponin-I" assay (Abbott Diagnostics), and of hs-cTnT with the "Troponin T hs" assay (Roche Diagnostics). URLs were calculated by using a non-parametric percentile method.

RESULTS

The 97.5th percentile URL for galectin-3 was 16 ng/mL in males and 17 ng/mL in females; the 99 th percentile URL for hs-cTnI was 39 ng/L in males and 24 ng/L in females; and the 99 th percentile URL for hs-cTnT was 14 ng/L in males and 11 ng/L in females. Those individuals with hs-cTnI values ≥ 15 ng/L (n=8) were different from those individuals with hs-cTnT values ≥ 10 ng/L (n=7). Of the 402 individuals, none had galectin-3 values below the limit of detection (LOD, <1.0 ng/mL), 290 (72%) had hs-cTnI values below the LOD (i.e., 1.9 ng/L), and 359 (89%) had hs-cTnT values below the LOD (i.e., 5.0 ng/L).

CONCLUSION

Plasma concentrations of galectin-3, hs-cTnI and hs-cTnT and corresponding 99 th percentile URLs were rather low in our cohort of healthy blood donors compared with previously published data. In our reference population, analyte plasma concentrations above the LOD were detectable in 100% of the individuals with the Abbott galectin-3 assay, but only in less than 50% for both the Abbott hs-cTnI assay and the Roche hs-cTnT assay.

Effect of Coronary Atherosclerosis and Myocardial Ischemia on Plasma Levels of High-Sensitivity Troponin T and NT-proBNP in Patients With Stable Angina

OBJECTIVE

Circulating levels of high-sensitivity cardiac troponin T (hs-cTnT) and N terminal pro brain natriuretic peptide (NT-proBNP) are predictors of prognosis in patients with coronary artery disease (CAD). We aimed at evaluating the effect of coronary atherosclerosis and myocardial ischemia on cardiac release of hs-cTnT and NT-proBNP in patients with suspected CAD.

APPROACH AND RESULTS

Hs-cTnT and NT-proBNP were measured in 378 patients (60.1±0.5 years, 229 males) with stable angina and unknown CAD enrolled in the Evaluation of Integrated Cardiac Imaging (EVINCI) study. All patients underwent stress imaging to detect myocardial ischemia and coronary computed tomographic angiography to assess the presence and characteristics of CAD. An individual computed tomographic angiography score was calculated combining extent, severity, composition, and location of plaques. In the whole population, the median (25-75 percentiles) value of plasma hs-cTnT was 6.17 (4.2-9.1) ng/L and of NT-proBNP was 61.66 (31.2-132.6) ng/L. In a multivariate model, computed tomographic angiography score was an independent predictor of the plasma hs-cTnT (coefficient 0.06, SE 0.02; P=0.0089), whereas ischemia was a predictor of NT-proBNP (coefficient 0.38, SE 0.12; P=0.0015). Hs-cTnT concentrations were significantly increased in patients with CAD with or without myocardial ischemia (P<0.005), whereas only patients with CAD and ischemia showed significantly higher levels of NT-proBNP (P<0.001).

CONCLUSIONS

In patients with stable angina, the presence and extent of coronary atherosclerosis is related with circulating levels of hs-cTnT, also in the absence of ischemia, suggesting an ischemia-independent mechanism of hs-cTnT release. Obstructive CAD causing myocardial ischemia is associated with increased levels of NT-proBNP.

Elevated Plasma Cardiac Troponin T Levels Caused by Skeletal Muscle Damage in Pompe Disease

Background—

Elevated plasma cardiac troponin T (cTnT) levels in patients with neuromuscular disorders may erroneously lead to the diagnosis of acute myocardial infarction or myocardial injury.

Methods and Results—

In 122 patients with Pompe disease, the relationship between cTnT, cardiac troponin I, creatine kinase (CK), CK-myocardial band levels, and skeletal muscle damage was assessed. ECG and echocardiography were used to evaluate possible cardiac disease. Patients were divided into classic infantile, childhood-onset, and adult-onset patients. cTnT levels were elevated in 82% of patients (median 27 ng/L, normal values <14 ng/L). Cardiac troponin I levels were normal in all patients, whereas CK-myocardial band levels were increased in 59% of patients. cTnT levels correlated with CK levels in all 3 subgroups ( P <0.001). None of the abnormal ECGs recorded in 21 patients were indicative of acute myocardial infarction, and there were no differences in cTnT levels between patients with and without (n=90) abnormalities on ECG (median 28 ng/L in both groups). The median left ventricular mass index measured with echocardiography was normal in all the 3 subgroups. cTnT mRNA expression in skeletal muscle was not detectable in controls but was strongly induced in patients with Pompe disease. cTnT protein was identified by mass spectrometry in patient-derived skeletal muscle tissue.

Conclusions—

Elevated plasma cTnT levels in patients with Pompe disease are associated with skeletal muscle damage, rather than acute myocardial injury. Increased cTnT levels in Pompe disease and likely other neuromuscular disorders should be interpreted with caution to avoid unnecessary cardiac interventions.

Pre-analytic variability in cardiovascular biomarker testing

The impact of laboratory medicine on clinical cardiology has dramatically increased over the years and a lot of cardiovascular biomarkers have been recently proposed. In order to avoid clinical mistakes, physicians should be well aware of all the aspects, which could affect the quality of laboratory results, remembering that pre-analytic variability is an often overlooked significant source of bias, determining the vast majority of laboratory errors. This review addresses the determinants of pre-analitycal variability in cardiovascular biomarker testing, focusing on the most widespread biomarkers, which are cardiac troponins and natriuretic peptides.