The multidimensional value of natriuretic peptides in heart failure, integrating laboratory and clinical aspects

Natriuretic peptides (NP) play an essential role in heart failure (HF) regulation, and their measurement has improved diagnostic and prognostic accuracy. Clinical symptoms and objective measurements, such as NP levels, should be included in the HF definition to render it more reliable and consistent among observers, hospitals, and healthcare systems. BNP and NT-proBNP are reasonable surrogates for cardiac disease, and their measurement is critical to early diagnosis and risk stratification of HF patients. NPs should be measured in all patients presenting with dyspnea or other symptoms suggestive of HF to facilitate early diagnosis and risk stratification. Both BNP and NT-proBNP are currently used for guided HF management and display comparable diagnostic and prognostic accuracy. Standardized cutoffs for each NP assay are essential for data comparison. The value of NP testing is recognized at various levels, including patient empowerment and education, analytical and operational issues, clinical HF management, and cost-effectiveness.

Differentiating Cardiac Troponin Levels During Cardiac Myosin Inhibition or Cardiac Myosin Activation Treatments: Drug Effect or the Canary in the Coal Mine?

PURPOSE OF REVIEW

Cardiac myosin inhibitors (CMIs) and activators are emerging therapies for hypertrophic cardiomyopathy (HCM) and heart failure with reduced ejection fraction (HFrEF), respectively. However, their effects on cardiac troponin levels, a biomarker of myocardial injury, are incompletely understood.

RECENT FINDINGS

In patients with HCM, CMIs cause substantial reductions in cardiac troponin levels which are reversible after stopping treatment. In patients with HFrEF, cardiac myosin activator (omecamtiv mecarbil) therapy cause modest increases in cardiac troponin levels which are reversible following treatment cessation and not associated with myocardial ischaemia or infarction. Transient changes in cardiac troponin levels might reflect alterations in cardiac contractility and mechanical stress. Such transient changes might not indicate cardiac injury and do not appear to be associated with adverse outcomes in the short to intermediate term. Longitudinal changes in troponin levels vary depending on the population and treatment. Further research is needed to elucidate mechanisms underlying changes in troponin levels.

Judging the clinical suitability of analytical performance of cardiac troponin assays

New millennium diagnostic criteria for acute myocardial infarction precipitated a revolutionary shift from an approach based primarily on electrocardiography and clinical symptoms to a strategy based on biomarkers, and preferably cardiac troponins (cTn) I and T. In the last 20 years, clinical recommendations have strengthened the role of cTn and led to the development of highly sensitive (hs-cTn) assays, which are now leading players in all current clinical practice guidelines. To optimize the clinical use of these hs-cTn assays, focus on their analytical aspects has become increasingly important, emphasizing the need for the establishment of suitable analytical performance by the definition and implementation of appropriate specifications. An accurate estimate of measurement uncertainty, together with the acquisition of the highest analytical quality when very low concentrations of hs-cTn are measured, are essential requirements and should represent a practical laboratory standard in assuring optimal clinical use. Additional goals for further improving the quality of laboratory information should be the establishment of robust data concerning biological variation of cTn and the resolution of practical challenges opposed to the harmonization of cTn I results obtained by differing commercial measuring systems.

Storage conditions, sample integrity, interferences, and a decision tool for investigating unusual high-sensitivity cardiac troponin results

The current definition of high-sensitivity cardiac troponin (hs-cTn) assays is laboratory-based and their analytical attributes and characteristics have drawn significant attention in the literature at least partly due to the lower concentration cut-offs and changes in concentrations (i.e., deltas) employed in different algorithms and pathways to manage patient care. We propose that pre-analytical conditions such as sample type, storage conditions, and other interferences may also have a significant impact on hs-cTn concentrations and clinical management. The purpose of this literature review is to provide a summary of important pre-analytical and interference studies affecting hs-cTn concentrations. A breakdown of the literature for the major diagnostic companies providing core laboratory instrumentation (i.e., Abbott, Beckman, Ortho, Roche, and Siemens) is also provided. Finally, three cases are highlighted where knowledge of pre-analytical factors aids the hs-cTn clinically discordant investigations. This review highlights the importance of pre-analytical variables, especially storage condition, sample handling, and blood tubes used (i.e., sample type) when interpreting hs-cTn assays. Additional studies are needed to further elaborate on pre-analytical variables (i.e., centrifugation, sample type, stability) and interferences for all hs-cTn assays in clinical use, as knowledge of these variables may aid in hs-cTn clinically discordant investigations.

Performance of the Abbott Architect Immuno-Chemiluminometric NT-proBNP Assay

Background: We evaluated the performance of the Abbott N-terminal pro-brain natriuretic peptide (NT-proBNP) assay against the Roche NT-proBNP immunoassay across two sites. Methods: Precision, linearity, and sensitivity studies were performed. A combined method of comparison and regression analysis was performed between the Roche and Abbott assays using samples from both sites (n = 494). To verify biotin interference, lyophilised biotin powder was reconstituted and spiked into serum samples at two medical decision levels (final concentration 500/4250 ng/mL) and compared to controls. NT-proBNP was also measured in anonymised leftover sera (n = 388) in a cardio-renal healthy population and stratified into three age bands—<50 (n = 145), 50−75 (n = 183) and >75 (n = 60). Results: Between-run precision (CV%) for NT-proBNP was 4.17/4.50 (139.5/142.0 pg/mL), 3.83/2.17 (521.6/506.3), and 4.60/2.51 (5053/4973), respectively. The assay was linear from 0.7−41,501 pg/mL. The limit of blank/quantitation was 1.2/7.9 pg/mL. The assay showed no interference from biotin up to 4250 ng/mL. Passing−Bablok regression analysis showed excellent agreement between the two assays (r = 0.999, 95% CI 0.999 to 0.999, p < 0.0001). The Roche assay had a slightly persistent, negative bias across different levels of NT-proBNP. ESC age cut-offs for diagnosing acute heart failure are applicable for the Abbott assay, with the median NT-proBNP of subjects < 50 years old at 43.0 pg/mL (range 4.9−456 pg/mL), 50−75 years old at 95.1 pg/mL (range 10.5−1079 pg/mL), and >75 years old at 173.1 pg/mL (range 23.2−1948 pg/mL). Conclusions: The Abbott Architect NT-proBNP assay has good performance that agrees with the manufacturer’s specifications. ESC/AHA recommended NT-proBNP age groups for acute heart failure diagnosis are applicable to this assay.

Troponin interference with special regard to macrocomplex formation

Biomarkers, such as troponin-T and troponin-I, are regarded as the gold standard laboratory parameter for diagnosing many cardiological diseases. These parameters have been approved for clinical use. Many cardiological guidelines recommend the analysis of troponins in the majority of cardiological disease diagnoses and to also gain prognostic information. Nonetheless, many medical circumstances could cause false troponin elevations. In this article, we focus on troponin artifacts, particularly macro-immune complex formation, as important interference factors. Therefore, we performed a literature search from 2006 to 06/2021.

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.

Pre-analytical considerations in biomarker research: focus on cardiovascular disease

Clinical biomarker research is growing at a fast pace, particularly in the cardiovascular field, due to the demanding requirement to provide personalized precision medicine. The lack of a distinct molecular signature for each cardiovascular derangement results in a one-size-fits-all diagnostic and therapeutic approach, which may partially explain suboptimal outcomes in heterogeneous cardiovascular diseases (e.g., heart failure with preserved ejection fraction). A multidimensional approach using different biomarkers is quickly evolving, but it is necessary to consider pre-analytical variables, those to which a biological sample is subject before being analyzed, namely sample collection, handling, processing, and storage. Pre-analytical errors can induce systematic bias and imprecision, which may compromise research results, and are easy to avoid with an adequate study design. Academic clinicians and investigators must be aware of the basic considerations for biospecimen management and essential pre-analytical recommendations as lynchpin for biological material to provide efficient and valid data.

Exploration of serum cardiac troponin I as a biomarker of cardiomyopathy in southern sea otters (Enhydra lutris nereis)

OBJECTIVE

To compare serum cardiac troponin I (cTnI) concentrations between sea otters with and without cardiomyopathy and describe 2 cases of cardiomyopathy with different etiologies.

ANIMALS

25 free-ranging southern sea otters (Enhydra lutris nereis) with (n = 14; cases) and without (11; controls) cardiomyopathy and 17 healthy managed southern sea otters from aquariums or rehabilitation centers (controls).

PROCEDURES

Serum cTnI concentration was measured in live sea otters. Histopathologic and gross necropsy findings were used to classify cardiomyopathy status in free-ranging otters; physical examination and echocardiography were used to assess health status of managed otters. Two otters received extensive medical evaluations under managed care, including diagnostic imaging, serial cTnI concentration measurement, and necropsy.

RESULTS

A significant difference in cTnI concentrations was observed between cases and both control groups, with median values of 0.279 ng/mL for cases and < 0.006 ng/mL for free-ranging and managed controls. A cutoff value of ≥ 0.037 ng/mL yielded respective sensitivity and specificity estimates for detection of cardiomyopathy of 64.3% and 90.9% for free-ranging cases versus free-ranging controls and 64.3% and 94.1% for free-ranging cases versus managed controls.

CONCLUSIONS AND CLINICAL RELEVANCE

Cardiomyopathy is a common cause of sea otter death that has been associated with domoic acid exposure and protozoal infection. Antemortem diagnostic tests are needed to identify cardiac damage. Results suggested that serum cTnI concentration has promise as a biomarker for detection of cardiomyopathy in sea otters. Serial cTnI concentration measurements and diagnostic imaging are recommended to improve heart disease diagnosis in managed care settings.

Potential pitfalls when interpreting plasma BNP levels in heart failure practice

B-type (or brain) natriuretic peptide (BNP) is synthesized in cardiac myocytes and released constitutively into the circulation. Pressure/volume overload, neurohumoral factors, cytokines, and ischemia enhance BNP gene expression, and then precursor proBNP is produced. It has been thought that proBNP is cleaved into active BNP molecule and inactive marker molecule NT-proBNP intracellularly by processing enzyme furin, and they are released into the circulation. However, recent studies have shown that considerable amount of uncleaved proBNP circulates in the blood. The commercially available BNP assay kits consist of two antibodies that sandwich the BNP molecule. Therefore, if proBNP is present, BNP assay kit cross-reacts to proBNP and measures it as BNP. Therefore, it should be noted that the current BNP value is proBNP plus BNP. BNP and NT-proBNP have been established as a biomarker for heart failure patients presenting dyspnea. But many pitfalls are present for interpreting the BNP value. For example, the presence of renal dysfunction, age, female sex, atrial fibrillation, inflammation, hyperthyroidism, use of sacubitril/valsartan, and macro-proBNPemia overestimate BNP value, whereas the presence of obesity, immediately after acute coronary syndrome onset, and pericardial effusion underestimate BNP value. In the management for heart failure patients, BNP plays an important role. Therefore, clinicians should note the pitfall of interpretation of BNP and we describe the mechanism involved.

High-sensitivity cardiac troponin assays for cardiovascular risk stratification in the general population

Cardiac troponins (cTns) I and T have long been the most successful cardiac-specific circulating biomarkers in cardiovascular (CV) medicine, having changed dramatically the diagnosis of acute myocardial infarction, while being independent predictors of outcome in several cardiac conditions and non-cardiac conditions. The latest-generation high-sensitivity (hs) cTn assays demonstrate both enhanced diagnostic performance and improved analytical performance, with the ability to measure detectable concentrations in a substantial proportion of the asymptomatic and presumably healthy populations. Given this unique analytical feature, recent evidence suggests that hs-cTn can be used for the stratification of CV risk in the general population. High-sensitivity cTn predicts future CV events, are responsive to preventive pharmacological or lifestyle interventions, change in parallel to risk modifications, and offer incremental risk prediction when added to well-established prognosticators. The implementation of CV risk stratification and prevention strategies incorporating hs-cTn requires further investigation to define the optimal target populations, timing of measurement, and preventive interventions.

Independent and combined effects of biotin and hemolysis on high-sensitivity cardiac troponin assays

OBJECTIVES

This study compared the independent and combined effects of hemolysis and biotin on cardiac troponin measurements across nine high-sensitivity cardiac troponin (hs-cTn) assays.

METHODS

Parallel cTn measurements were made in pooled lithium heparin plasma spiked with hemolysate and/or biotin using nine hs-cTn assays: Abbott Alinity, Abbott ARCHITECT i2000, Beckman Access 2, Ortho VITROS XT 7600, Siemens Atellica, Siemens Centaur, Siemens Dimension EXL cTnI, and two Roche Cobas e 411 Elecsys Troponin T-hs cTnT assays (outside US versions, with and without increased biotin tolerance). Absolute and percent cTn recovery relative to two baseline concentrations were determined in spiked samples and compared to manufacturer's claims.

RESULTS

All assays except the Ortho VITROS XT 7600 showed hemolysis and biotin interference thresholds equivalent to or greater than manufacturer's claims. While imprecision confounded analysis of Ortho VITROS XT 7600 data, evidence of biotin interference was lacking. Increasing biotin concentration led to decreasing cTn recovery in three assays, specifically both Roche Cobas e 411 Elecsys Troponin T-hs assays and the Siemens Dimension EXL. While one of the Roche assays was the most susceptible to biotin among the nine studied, a new version showed reduced biotin interference by approximately 100-fold compared to its predecessor. Increasing hemolysis also generally led to decreasing cTn recovery for susceptible assays, specifically the Beckman Access 2, Ortho VITROS XT 7600, and both Roche Cobas e 411 Elecsys assays. Equivalent biotin and hemolysis interference thresholds were observed at the two cTn concentrations considered for all but two assays (Beckman Access 2 and Ortho VITROS XT 7600). When biotin and hemolysis were present in combination, biotin interference thresholds decreased with increasing hemolysis for two susceptible assays (Roche Cobas e 411 Elecsys and Siemens Dimension EXL).

CONCLUSIONS

Both Roche Cobas e 411 Elecsys as well as Ortho VITROS XT assays were susceptible to interference from in vitro hemolysis at levels routinely encountered in clinical laboratory samples (0-3 g/L free hemoglobin), leading to falsely low cTn recovery up to 3 ng/L or 13%. While most assays are not susceptible to biotin at levels expected with over-the-counter supplementation, severely reduced cTn recovery is possible at biotin levels of 10-2000 ng/mL (41-8,180 nmol/L) for some assays. Due to potential additive effects, analytical interferences should not be considered in isolation.

Evaluating the performance of an updated high-sensitivity troponin T assay with increased tolerance to biotin

OBJECTIVES

Biotin >20 ng/mL may interfere with the Elecsys^® Troponin T-high sensitive assay (cTnT-hs; Roche Diagnostics International Ltd). We evaluated the performance of an updated assay, cTnT-hs*, which was designed to reduce biotin interference.

METHODS

cTnT-hs* assay performance was assessed using up to two applications (18 min/9 min) on three analyzers (cobas e 411/cobas e 601/cobas e 801). Biotin interference was determined by measuring recovery in an 11-sample series dilution with biotin ranging from 0-3600 ng/mL. Repeatability/reproducibility were evaluated in five serum sample pools (n=75 each). Method comparisons tested: cTnT-hs* vs. cTnT-hs (18 min/cobas e 601); cTnT-hs* assay 18 vs. 9 min (cobas e 601); cTnT-hs* (18 min) on cobas e 601 vs. cobas e 411 and cobas e 601 vs. cobas e 801. Concordance at the 99th percentile decision limit between cTnT-hs* and cTnT-hs (9 min/cobas e 601) was calculated using 300 lithium-heparin plasma samples and a 14 ng/L assay cutoff.

RESULTS

cTnT-hs* assay (18 min/cobas e 601) recovery was ≥96% for biotin ≤1250 ng/mL. Across all applications/analyzers, coefficients of variation for repeatability/reproducibility with the cTnT-hs* assay were <5% in most serum sample pools (mean cardiac troponin T: 8.528-9484 ng/L). High correlation (Pearson's r=1.000) was demonstrated for all method comparisons. Concordance at the 99th percentile decision limit was high between the cTnT-hs* and cTnT-hs assays.

CONCLUSIONS

The updated cTnT-hs* assay may provide greater tolerance to biotin interference, and shows good analytical and clinical agreement/concordance with the previous cTnT-hs assay.

Analytical assessment of ortho clinical diagnostics high-sensitivity cardiac troponin I assay

Objectives

To analytically evaluate Ortho Clinical Diagnostics VITROS high-sensitivity cardiac troponin I (hs-cTnI) assay in specific matrices with comparison to other hs-cTn assays.

Methods

The limit of detection (LoD), imprecision, interference and stability testing for both serum and lithium heparin (Li-Hep) plasma for the VITROS hs-cTnI assay was determined. We performed Passing-Bablok regression analyses between sample types for the VITROS hs-cTnI assay and compared them to the Abbott ARCHITECT, Beckman Access and the Siemens ADVIA Centaur hs-cTnI assays. We also performed Receiver-operating characteristic curve analyses with the area under the curve (AUC) determined in an emergency department (ED)-study population (n=131) for myocardial infarction (MI).

Results

The VITROS hs-cTnI LoD was 0.73 ng/L (serum) and 1.4 ng/L (Li-Hep). Stability up to five freeze-thaws was observed for the Ortho hs-cTnI assay, with the analyte stability at room temperature in serum superior to Li-Hep with gross hemolysis also affecting Li-Hep plasma hs-cTnI results. Comparison of Li-Hep to serum concentrations (n=202), yielded proportionally lower concentrations in plasma with the VITROS hs-cTnI assay (slope=0.85; 95% confidence interval [CI]:0.83-0.88). In serum, the VITROS hs-cTnI concentrations were proportionally lower compared to other hs-cTnI assays, with similar slopes observed between assays in samples frozen <-70 °C for 17 years (ED-study) or in 2020. In the ED-study, the VITROS hs-cTnI assay had an AUC of 0.974 (95%CI:0.929-0.994) for MI, similar to the AUCs of other hs-cTn assays.

Conclusions

Lack of standardization of hs-cTnI assays across manufacturers is evident. The VITROS hs-cTnI assay yields lower concentrations compared to other hs-cTnI assays. Important differences exist between Li-Hep plasma and serum, with evidence of stability and excellent clinical performance comparable to other hs-cTn assays.

High-sensitivity methods for cardiac troponins: The mission is not over yet

The measurement of cardiac troponin (cTn) is recommended by all guidelines as the gold standard for the differential diagnosis of Acute Coronary Syndromes. The aim of this review is to discuss in details some key issues regarding both analytical and clinical characteristics of the high-sensitivity methods for cTn (hs-cTn), which are still considered controversial or unresolved. In particular, the major clinical concern regarding hs-cTn methods is the difficulty to differentiate the pathophysiological mechanism responsible for biomarker release from cardiomyocytes after reversible or irreversible injury, respectively. Indeed, recent experimental and clinical studies have demonstrated that different circulating forms of cTnI and cTnT can be respectively measured in plasma samples of patients with reversible or irreversible myocardial injury. Accordingly, a new generation of hs-Tn methods should be set up, based on immunometric immunoassays or chromatographic techniques, specific for circulating peptide forms more characteristics for reversible or irreversible myocardial injury. It is conceivable that this new generation of hs-cTn methods will complete the mission regarding the laboratory tests for specific cardiac biomarkers, started more than 20 years ago, which has already revolutionized the diagnosis, prognosis and management of patients with cardiac diseases.

Fast 0/1-h algorithm for detection of NSTEMI: are current high-sensitivity cardiac troponin assays fit for purpose? An EQA-based evaluation

Background High-sensitivity cardiac troponin T/I (hs-cTnT/I) assays have improved analytical sensitivity for the detection of myocardial infarction (MI). To gain clinical specificity and sensitivity, interpretation of changes in cTn concentrations over time is crucial. The 2015 ESC NSTEMI guideline defines absolute delta values as additional rule-in and rule-out criteria for MI. A critical assumption for application of this rule is that total analytical imprecision within the delta period, including inter-instrument bias, is comparable to analytical imprecision in the validation studies. Methods Data from the Dutch External Quality Assessment Scheme (EQAS) were used to calculate inter-instrument bias and estimate imprecision for the measuring range where the proposed delta values are relevant: for Roche Elecsys hs-cTnT, 5-52 and 5-12 ng/L; for Abbott Architect hs-cTnI, 2-52 and 2-5 ng/L for rule-in and rule-out, respectively. Results For Elecsys, the median inter-instrument bias is 0.3 ng/L (n = 33 laboratories), resulting in reference change values (RCVs) of 3.0 and 1.7 ng/L, respectively, for rule-in and rule-out with imprecision as claimed by the manufacturer. With RCVs smaller than the guideline's delta thresholds, 100% of the laboratories have adequate specifications. RCVs for rule-in/rule-out increased to 4.6 ng/L/2.5 ng/L, respectively, with individual imprecisions as estimated from EQA data, resulting in 64% and 82% of laboratories with adequate specifications. For Architect, 40% of instruments (n = 10) might falsely qualify the result as clinically relevant; hence, inter-instrument bias could not be determined. Conclusions We advise laboratories that use the fast 0/1-h algorithm to introduce stringent internal quality procedures at the relevant/low concentration level, especially when multiple analyzers are randomly used.

Clinical risk assessment of biotin interference with a high-sensitivity cardiac troponin T assay

Objectives

Biotin >20.0 ng/mL (81.8 nmol/L) can reduce Elecsys® Troponin T Gen 5 (TnT Gen 5; Roche Diagnostics) assay recovery, potentially leading to false-negative results in patients with suspected acute myocardial infarction (AMI). We aimed to determine the prevalence of elevated biotin and AMI misclassification risk from biotin interference with the TnT Gen 5 assay.

Methods

Biotin was measured using an Elecsys assay in two cohorts: (i) 797 0-h and 646 3-h samples from 850 US emergency department patients with suspected acute coronary syndrome (ACS); (ii) 2023 random samples from a US laboratory network, in which biotin distributions were extrapolated for higher values using pharmacokinetic modeling. Biotin >20.0 ng/mL (81.8 nmol/L) prevalence and biotin 99th percentile values were calculated. AMI misclassification risk due to biotin interference with the TnT Gen 5 assay was modeled using different assay cutoffs and test timepoints.

Results

ACS cohort: 1/797 (0.13%) 0-h and 1/646 (0.15%) 3-h samples had biotin >20.0 ng/mL (81.8 nmol/L); 99th percentile biotin was 2.62 ng/mL (10.7 nmol/L; 0-h) and 2.38 ng/mL (9.74 nmol/L; 3-h). Using conservative assumptions, the likelihood of false-negative AMI prediction due to biotin interference was 0.026% (0-h result; 19 ng/L TnT Gen 5 assay cutoff). US laboratory cohort: 15/2023 (0.74%) samples had biotin >20.0 ng/mL (81.8 nmol/L); 99th percentile biotin was 16.6 ng/mL (68.0 nmol/L). Misclassification risk due to biotin interference (19 ng/L TnT Gen 5 assay cutoff) was 0.025% (0-h), 0.0064% (1-h), 0.00048% (3-h), and <0.00001% (6-h).

Conclusions

Biotin interference has minimal impact on the TnT Gen 5 assay’s clinical utility, and the likelihood of false-negative AMI prediction is extremely low.

Atherosclerotic Cardiovascular Disease Risk Stratification Based on Measurements of Troponin and Coronary Artery Calcium

BACKGROUND

Low values of high-sensitivity cardiac troponin (hs-cTn) and coronary artery calcium (CAC) scores of zero are associated with a low risk for atherosclerotic cardiovascular disease (ASCVD).

OBJECTIVES

The purpose of this study was to evaluate baseline hs-cTnT and CAC in relation to ASCVD.

METHODS

Baseline hs-cTnT (limit of detection [LoD] 3 ng/l) and CAC measurements were analyzed across participants age 45 to 84 years without clinical cardiovascular disease from the prospective MESA (Multi-Ethnic Study of Atherosclerosis) in relationship to incident ASCVD.

RESULTS

Among 6,749 participants, 1,002 ASCVD events occurred during a median follow-up of 15 years. Participants with detectable CAC (20.1 vs. 5.0 events per 1,000 person-years; adjusted hazard ratio [HR]: 2.35; 95% confidence interval [CI]: 2.0 to 2.76; p < 0.001) and detectable hs-cTnT (15.4 vs. 5.2 per 1,000 person-years; adjusted HR: 1.47; 95% CI: 1.21 to 1.77; p < 0.001) had higher rates of ASCVD than those with undetectable results. Individuals with undetectable hs-cTnT (32%) had similar risk for ASCVD as did those with a CAC of zero (50%) (5.2 vs. 5.0 per 1,000 person-years). Together, hs-cTnT and CAC (discordance 38%) resulted in the following ASCVD event rates: hs-cTnT < LoD/CAC = 0: 2.8 per 1,000 person-years (reference), hs-cTnT ≥ LoD/CAC = 0: 6.8 per 1,000 person-years (HR: 1.59; 95% CI: 1.17 to 2.16; p = 0.003), hs-cTnT < LoD/CAC > 0: 11.1 per 1,000 person-years (HR: 2.74; 95% CI: 1.96 to 3.83; p < 0.00001), and hs-cTnT ≥ LoD/CAC > 0: 22.6 per 1,000 person-years (HR: 3.50; 95% CI: 2.60 to 4.70; p < 0.00001).

CONCLUSIONS

An undetectable hs-cTnT identifies patients with a similar, low risk for ASCVD as those with a CAC score of zero. The increased risk among those with discordant results supports their conjoined use for risk prediction.

High sensitivity, contemporary and point-of-care cardiac troponin assays: educational aids developed by the IFCC Committee on Clinical Application of Cardiac Bio-Markers

The International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) formed a Task Force on the Application of Cardiac Bio-markers (TF-CB) in 2008, re-designated in 2018 as a committee (C-CB), to produce educational materials on cardiac biomarkers. Established in June 2017, definitive tables covering the majority of high-sensitivity, contemporary and point-of-care (POC) cTn assays have been developed by the C-CB and are available on the IFCC website. These tables provide extensive information about assays' analytical characteristics and encompass information on diagnostic discriminants, particularly the 99th percentiles, as provided by the manufacturers.

A Multicenter Assessment of the Sensitivity and Specificity for a Single High-Sensitivity Cardiac Troponin Test at Emergency Department Presentation for Hospital Admission

Background

Studies have illustrated how a low or undetectable high-sensitivity cardiac troponin (hs-cTn) concentration at emergency department (ED) presentation can rule out myocardial infarction (MI). A problem with using an undetectable hs-cTn cutoff is that this value may be defined differently among hospitals and is also difficult to monitor. In the present study, we assess the diagnostic performance of a clinical chemistry score (CCS) vs hs-cTn alone in the presentation blood sample in the ED for patient hospital admission in a multicenter setting.

Methods

From January 1 to June 30, 2018, consecutive patients with random glucose, creatinine (for an estimated glomerular filtration rate calculation), and hs-cTnI (Abbott, 2 hospitals, Hamilton, Ontario, n = 10496) or hs-cTnT (Roche, 4 hospitals, Calgary, Alberta, n = 25177) were assessed for hospital admission with the CCS (range of scores, 0–5) or hs-cTn alone. Sensitivity, specificity, predicative values, and likelihood ratios were calculated for a CCS of 0 and 5 and for hs-cTn alone (hs-cTnI cutoffs, 5 and 26 ng/L; hs-cTnT cutoffs, 6 and 14 ng/L).

Results

The CCS of 0 (CCS &lt;1) identified approximately 10% of all patients as low risk and had a sensitivity for hospital admission of nearly 98% as compared to &lt;93% when hs-cTnT (&lt;6 ng/L) or hs-cTnI (&lt;5 ng/L) cutoffs alone were used. A CCS ≥5 had a specificity for hospital admission &gt;95%, with approximately 14% of patients at high risk.

Conclusions

An ED disposition (admit or send home) using the presentation blood sample could occur in nearly 25% of all patients by use of the CCS.

Educational Recommendations on Selected Analytical and Clinical Aspects of Natriuretic Peptides with a Focus on Heart Failure: A Report from the IFCC Committee on Clinical Applications of Cardiac Bio-Markers

The IFCC Committee on Clinical Applications of Cardiac Bio-Markers (C-CB) has directives and initiatives focused on providing evidence-based educational resources to aid and improve understanding around key analytical and clinical aspects of cardiac biomarkers used in clinical practice and the research setting. As a task force, we have previously published position statements and recommendations focused on use and analytical aspects of high-sensitivity cardiac troponin assays. The current educational document is the first from the C-CB highlighting important biochemical, analytical, and clinical aspects as they relate to the natriuretic peptides (NPs), including B-type natriuretic peptide (BNP) and N-terminal pro–B-type natriuretic peptide (NT-proBNP), with a focus on heart failure.