The sensitivity of cardiac markers: an evidence-based approach

Circulating Biomarkers for Monitoring Chemotherapy-Induced Cardiotoxicity in Children

Most commonly diagnosed cancer pathologies in the pediatric population comprise leukemias and cancers of the nervous system. The percentage of cancer survivors increased from approximatively 50% to 80% thanks to improvements in medical treatments and the introduction of new chemotherapies. However, as a consequence, heart disease has become the main cause of death in the children due to the cardiotoxicity induced by chemotherapy treatments. The use of different cardiovascular biomarkers, complementing data obtained from electrocardiogram, echocardiography cardiac imaging, and evaluation of clinical symptoms, is considered a routine in clinical diagnosis, prognosis, risk stratification, and differential diagnosis. Cardiac troponin and natriuretic peptides are the best-validated biomarkers broadly accepted in clinical practice for the diagnosis of acute coronary syndrome and heart failure, although many other biomarkers are used and several potential markers are currently under study and possibly will play a more prominent role in the future. Several studies have shown how the measurement of cardiac troponin (cTn) can be used for the early detection of heart damage in oncological patients treated with potentially cardiotoxic chemotherapeutic drugs. The advent of high sensitive methods (hs-cTnI or hs-cTnT) further improved the effectiveness of risk stratification and monitoring during treatment cycles.

Cardiac Biomarkers in Patients with Acute Pulmonary Embolism

Pulmonary embolism is a frequent and potentially fatal disease. The major challenge of initial management lies in prognostic stratification. Since 2014, the European recommendations on the diagnosis and management of acute pulmonary embolism are based on assessing the risk stratification regarding hemodynamic status first, then on a combined risk assessment model using a clinical score, an imaging evaluation of right heart size and the concentration of a serum cardiac biomarker. Usual biomarkers cover cardiac ischemia (troponin and derivates) and dilatation (BNP and derivates). The aim of this review is to offer a practical update on the role of the Troponins and BNPs families of biomarkers and the prognosis of pulmonary embolism, and furthermore, to provide a brief overview of their place in current management.

High-Sensitivity Troponin: A Review on Characteristics, Assessment, and Clinical Implications

The use of high-sensitivity cardiac troponin (hs-cTn) assays has become part of the daily practice in most of the laboratories worldwide in the initial evaluation of the typical chest pain. Due to their early surge, the use of hs-cTn may reduce the time needed to recognise myocardial infarctions (MI), which is vital for the patients presenting in the emergency departments for chest pain. The latest European Society of Cardiology Guidelines did not only recognise their central role in the diagnosis algorithm but also recommended their use for rapid rule-in/rule-out of MI. High-sensitivity cardiac troponins are also powerful prognostic markers for long-term events and mortality, not only in a wide spectrum of other cardiovascular diseases (CVD) but also in several non-CVD pathologies. Moreover, these biomarkers became a powerful tool in special populations, such as paediatric patients and, most recently, COVID-19 patients. Although highly investigated, the assessment and interpretation of the hs-cTn changes are still challenging in the patients with basal elevation such as CKD or critically ill patients. Moreover, there are still various analytical characteristics not completely understood, such as circadian or sex variability, with major clinical implications. In this context, the present review focuses on summarizing the most recent research in the current use of hs-cTn, with a main consideration for its role in the diagnosis of MI but also its prognostic value. We have also carefully selected the most important studies regarding the challenges faced by clinicians from different specialties in the correct interpretation of this biomarker. Moreover, future perspectives have been proposed and analysed, as more research and cross-disciplinary collaboration are necessary to improve their performance.

Cardiac Graft Assessment in the Era of Machine Perfusion: Current and Future Biomarkers

Heart transplantation remains the treatment of reference for patients experiencing end‐stage heart failure; unfortunately, graft availability through conventional donation after brain death is insufficient to meet the demand. Use of extended‐criteria donors or donation after circulatory death has emerged to increase organ availability; however, clinical protocols require optimization to limit or prevent damage in hearts possessing greater susceptibility to injury than conventional grafts. The emergence of cardiac ex situ machine perfusion not only facilitates the use of extended‐criteria donor and donation after circulatory death hearts through the avoidance of potentially damaging ischemia during graft storage and transport, it also opens the door to multiple opportunities for more sensitive monitoring of graft quality. With this review, we aim to bring together the current knowledge of biomarkers that hold particular promise for cardiac graft evaluation to improve precision and reliability in the identification of hearts for transplantation, thereby facilitating the safe increase in graft availability. Information about the utility of potential biomarkers was categorized into 5 themes: (1) functional, (2) metabolic, (3) hormone/prohormone, (4) cellular damage/death, and (5) inflammatory markers. Several promising biomarkers are identified, and recommendations for potential improvements to current clinical protocols are provided.

Adenosine 2A Receptor Activation Attenuates Ischemia Reperfusion Injury During Extracorporeal Cardiopulmonary Resuscitation

OBJECTIVE

We tested the hypothesis that systemic administration of an A2AR agonist will reduce multiorgan IRI in a porcine model of ECPR.

SUMMARY BACKGROUND DATA

Advances in ECPR have decreased mortality after cardiac arrest; however, subsequent IRI contributes to late multisystem organ failure. Attenuation of IRI has been reported with the use of an A2AR agonist.

METHODS

Adult swine underwent 20 minutes of circulatory arrest, induced by ventricular fibrillation, followed by 6 hours of reperfusion with ECPR. Animals were randomized to vehicle control, low-dose A2AR agonist, or high-dose A2AR agonist. A perfusion specialist using a goal-directed resuscitation protocol managed all the animals during the reperfusion period. Hourly blood, urine, and tissue samples were collected. Biochemical and microarray analyses were performed to identify differential inflammatory markers and gene expression between groups.

RESULTS

Both the treatment groups demonstrated significantly higher percent reduction from peak lactate after reperfusion compared with vehicle controls. Control animals required significantly more fluid, epinephrine, and higher final pump flow while having lower urine output than both the treatment groups. The treatment groups had lower urine NGAL, an early marker of kidney injury (P = 0.01), lower plasma aspartate aminotransferase, and reduced rate of troponin rise (P = 0.01). Pro-inflammatory cytokines were lower while anti-inflammatory cytokines were significantly higher in the treatment groups.

CONCLUSIONS

Using a novel and clinically relevant porcine model of circulatory arrest and ECPR, we demonstrated that a selective A2AR agonist significantly attenuated systemic IRI and warrants clinical investigation.

Heart-type fatty acid-binding protein (H-FABP) as an early diagnostic biomarker in patients with acute chest pain

BACKGROUND

Heart-type fatty acid-binding protein (H-FABP) is an emerging biomarker, which was found to be sensitive for the early diagnosis of acute myocardial infarction (AMI). We prospectively investigated the usefulness of H-FABP determination for the evaluation of acute chest pain in patients arriving at the emergency department.

METHODS

Fifty-four patients presenting with acute ischemic chest pain were evaluated. H-FABP was estimated at admission using latex-enhanced immunoturbidimetric assay. Serial cardiac troponin I (cTnI), creatinine kinase-MB (CK-MB) determination, ischemia workup with stress testing, and/or coronary angiogram (CAG) were performed according to standard protocols.

RESULTS

The sensitivity and specificity of H-FABP was 89.7% and 68%, for cTnI it was 62.1% and 100%, and for CK-MB it was 44.8% and 92%, respectively for diagnosis of AMI. The sensitivity of H-FABP was found to be far superior to initial cTnI and CK-MB, for those seen within 6h (100% vs. 46.1%, 33% respectively). On further evaluation of patients with positive H-FABP and negative cTnI, 71.4% of the patients had significant lesion on CAG, indicating ischemic cause of H-FABP elevation. Six patients with normal cTnI and CK-MB with high H-FABP had ST elevation on subsequent ECGs and were taken for primary angioplasty.

CONCLUSION

H-FABP is a highly sensitive biomarker for the early diagnosis of AMI. H-FABP as early marker and cTnI as late marker would be the ideal combination to cover the complete diagnostic window for AMI. Detection of myocardial injury by H-FABP may also be applied in patients with unstable angina. H-FABP can also be used as a marker for early detection of STEMI before the ECG changes become apparent.

Role of copeptin in dual-cardiac marker strategy for patients with chest pain presented to ED

OBJECTIVE

The objective of the study is to evaluate the role of copeptin in the diagnosis of acute coronary syndrome (ACS) and its role in dual-cardiac marker diagnostic strategy with troponin.

DESIGN

A prospective cohort study was carried out from May 2012 to October 2012.

SETTING

The study was conducted at the emergency department (ED) of a public hospital in a cluster of Hong Kong.

METHODS

Patients aged at least 18 years presented with chest pain to ED who have intermediate or high likelihood of ACS were included. All patients had blood taken in the ED for copeptin and troponin I. The adjudicated diagnoses of ACS were made by 2 independent physicians based on the universal definition. Diagnostic characteristics were calculated. Receiver operating characteristic curves were created. Areas under the curves were compared for copeptin, troponin I, and dual-marker strategy with copeptin and troponin I.

RESULTS

A total of 637 patients were recruited. Seventy-eight had been diagnosed to be ACS. The negative predictive value of copeptin for ACS was 0.881 (0.849-0.907) compared with troponin I, 0.937 (0.913-0.956). The areas under the receiver operating characteristic curves of copeptin, troponin I, and dual-marker strategy were 0.68, 0.859, and 0.880, respectively.

CONCLUSIONS

Addition of copeptin to troponin does not have significant improvement of the diagnostic accuracy of ACS in patients presented with chest pain.

Role of MIF in myocardial ischaemia and infarction: insight from recent clinical and experimental findings

First discovered in 1966 as an inflammatory cytokine, MIF (macrophage migration inhibitory factor) has been extensively studied for its pivotal role in a variety of inflammatory diseases, including rheumatoid arthritis and atherosclerosis. Although initial studies over a decade ago reported increases in circulating MIF levels following acute MI (myocardial infarction), the dynamic changes in MIF and its pathophysiological significance following MI have been unknown until recently. In the present review, we summarize recent experimental and clinical studies examining the diverse functions of MIF across the spectrum of acute MI from brief ischaemia to post-infarct healing. Following an acute ischaemic insult, MIF is rapidly released from jeopardized cardiomyocytes, followed by a persistent MIF production and release from activated immune cells, resulting in a sustained increase in circulating levels of MIF. Recent studies have documented two distinct actions of MIF following acute MI. In the supra-acute phase of ischaemia, MIF mediates cardioprotection via several distinct mechanisms, including metabolic activation, apoptosis suppression and antioxidative stress. In prolonged myocardial ischaemia, however, MIF promotes inflammatory responses with largely detrimental effects on cardiac function and remodelling. The pro-inflammatory properties of MIF are complex and involve MIF derived from cardiac and immune cells contributing sequentially to the innate immune response evoked by MI. Emerging evidence on the role of MIF in myocardial ischaemia and infarction highlights a significant potential for the clinical use of MIF agonists or antagonists and as a unique cardiac biomarker.

Diagnosis of Non-ST-Elevation Acute Coronary Syndrome by the Measurement of Heart-Type Fatty Acid Binding Protein in Serum: A Prospective Case Control Study

A prospective case control study was undertaken to evaluate the diagnostic performance of serum heart-type fatty acid binding protein (HFABP) in comparison to cardiac TnT and TnI in 33 patients admitted with chest pain, diagnosed as NSTE-ACS (non ST elevation acute coronary syndrome) and 22 healthy controls. Area under the receiver operating curve (AUC) was highest for H-FABP (AUC 0.79; 95% CI 0.66-0.89) versus cTnI (AUC 0.73; 95% CI 0.59-0.84) and cTnT (AUC 0.71; 95% CI 0.57-0.83). The H-FABP level above 6.5 ng/mL showed 56.7% (CI 37.4-74.5) sensitivity, 0.5 (95% CI 0.3-0.7) negative likelihood ratio (-LR), 100% (CI 84.6-100.0) specificity, and 100% (CI 79.4-100.0) positive predictive value (PPV), 62.9% (CI 44.9-78.5) negative predictive value (NPV). cTnI level above 0.009 μg/L had 40% (CI 22.7-59.4) sensitivity, 0.6 (95% CI 0.4-0.8) -LR, 100% (CI 84.6-100.0) specificity, 100% (CI 73.5-100.0) PPV, and 55% (CI 38.5-70.7) NPV. cTnT showed 46.7% (CI 28.3-65.7) sensitivity, 0.5 (95% CI 0.4-0.7) -LR, 100% (CI 84.6-100.0) specificity, 100% (CI 76.8-100.0) PPV, and 57.9% (CI 40.8-73.7) NPV at level above 9 μg/L. +LR were 12.5 (95% CI 1.8-86.8), 1.7 (95% CI 1.0-3.0), and 1.2 (95% CI 0.8-1.9) for H-FABP, cTnI, and cTnT respectively. In conclusion measurement of H-FABP is a valuable tool in the early diagnosis of patients with chest pain (6-8 hrs) and seems to be a preferred biomarker in the differential diagnosis of NSTE-ACS. More studies are needed to determine whether serum H-FABP further improves diagnostic performance.

Cardiogoniometry as a diagnostic tool in patients with acute coronary syndromes: results of the CGM@ACS trial

BACKGROUND

Cardiogoniometry (CGM) is a novel electrocardiac method utilising computer-assisted three-dimensional information on cardiac potentials.

OBJECTIVE

To investigate the potential of CGM in discriminating non-ST-segment elevation acute coronary syndrome (NSTE-ACS) and relevant coronary stenosis upon hospital admission by prospectively comparing its sensitivity, specificity and accuracy against those of a single troponin test and a 12-lead ECG performed on admission

DESIGN

A multicenter prospective observational trial.

SETTING

Eight interventional cardiac centres in Germany.

PATIENTS

A cohort of 216 patients (mean age 67 years, 34.7 % female) who presented with acute chest pain or dyspnoea without ST-segment elevation and were scheduled for coronary angiography within 72 h of admission.

INTERVENTION

Pre-angiography screening by CGM, troponin test, 12-lead ECG MAIN OUTCOME MEASURES: ECG, troponin and CGM on admission compared with final diagnosis of NSTE-ACS or relevant diameter stenosis ≥70 % verified by an independent review board and an angiographic core laboratory.

RESULTS

NSTE-ACS was finally confirmed in 162 cases, whereas the remaining 54 cases without proof of NSTE-ACS served as controls. Diagnostic sensitivity for NSTE-ACS was 28, 50 and 69 % and specificity 78, 96 and 54 % for first ECG, serial troponin and first CGM, respectively. Accuracy was 40, 62 and 65 %. The sensitivity of the tests to detect relevant coronary stenosis (n = 126) was 32, 53 and 74 %, respectively. The sensitivity of CGM to detect NSTE-ACS (65 %) or relevant stenosis (71 %) was high even in patients with normal troponin and ECG.

CONCLUSIONS

CGM can detect NSTE-ACS at first medical contact. CGM in conjunction with traditional markers, 12-lead ECG and troponin may effectively aid early decision making in patients presenting with acute chest pain.

Diagnostic accuracy of heart fatty acid binding protein (H-FABP) and glycogen phosphorylase isoenzyme BB (GPBB) in diagnosis of acute myocardial infarction in patients with acute coronary syndrome

INTRODUCTION

This study aimed to assess whether heart fatty acid-binding protein (H-FABP) and glycogen phosphorylase isoenzyme BB (GPBB) could be used for the accurate diagnosis of acute myocardial infarction (AMI) in acute coronary syndrome (ACS) patients.

MATERIALS AND METHODS

The study included 108 ACS patients admitted to a coronary unit within 3 h after chest pain onset. AMI was distinguished from unstable angina (UA) using a classical cardiac troponin I (cTnI) assay. H-FABP and GPBB were measured by ELISA on admission (0 h) and at 3, 6, 12, and 24 h after admission; their accuracy to diagnose AMI was assessed using statistical methods.

RESULTS

From 92 patients with ACS; 71 had AMI. H-FABP and GPBB had higher peak value after 3 h from admission than cTnI (P = 0.001). Both markers normalized at 24 h. The area under the receiver operating characteristic curves was significantly greater for both markers in AMI patients than in UA patients at all time points tested, including admission (P < 0.001). At admission, the H-FABP (37%) and GPBB (40%) sensitivities were relatively low. They increased at 3 and 6 h after admission for both markers and decreased again after 24 h. It was 40% for H-FABP and approximately 2-times lower for GPBB (P < 0.01). In AMI patients, both biomarkers had similar specificities, positive- and negative-predictive values, positive and negative likelihood ratios, and risk ratios for AIM.

CONCLUSION

H-FABP and GPBB can contribute to early AMI diagnosis and can distinguish AMI from UA.

MicroRNAs as biomarkers for myocardial infarction

MicroRNAs (miRs) are short non-coding RNA molecules involved in post-transcriptional gene regulation by binding to the 3' untranslated region of a messenger RNA (mRNA), thereby inhibiting the translation or inducing mRNA destabilization. MiRs are generally considered to act as intracellular mediators essential for normal cardiac function, and their deregulated expression profiles have been associated with cardiovascular diseases. Recent studies have revealed the existence of freely circulating miRs in human peripheral blood, which are present in a stable nature. This has raised the possibility that miRs may be released in the circulation and can serve as novel diagnostic markers for acute or chronic human disorders, including myocardial infarction (MI). This review summarizes the recent findings of miRs that fulfill the criteria of candidate biomarkers for MI.

Heart fatty acid-binding protein in combination with the 80-lead body surface potential map improves early detection of acute myocardial infarction in patients who are cardiac troponin T-negative at presentation

Of patients who present with ischemic-type chest pain and a negative cardiac troponin T (cTnT) at first medical contact, there are patients at a very early stage of infarction. The aim of this research was to assess heart fatty acid-binding protein (H-FABP), a novel marker of myocyte necrosis, in combination with the 80-lead body surface potential map (BSPM) in the early diagnosis of acute myocardial infarction (AMI).

METHODS

In this prospective study, consecutive patients presenting with acute ischemic-type chest pain between 2003 and 2006 were enrolled. At first medical contact, blood was sampled for cTnT and H-FABP; in addition, a 12-lead electrocardiogram (ECG) and BSPM were recorded. A second cTnT was sampled 12 hours or more after presentation. Peak cTnT 0.03 μg/L or higher diagnosed AMI. Elevated H-FABP was 5 ng/mL or higher. A cardiologist blinded to both the clinical details and 12-lead ECG interpreted the BSPM.

RESULTS

Enrolled were 407 patients (age 62 ± 13 years; 70% men). Of these 407, 180 had cTnT less than 0.03 μg/L at presentation. Acute myocardial infarction occurred in 52 (29%) of 180 patients. Of these 180 patients, 27 had ST-segment elevation (STE) on ECG, 104 had STE on BSPM (sensitivity, 88%; specificity, 55%), and 95 (53%) had H-FABP elevation. The proportion with elevated H-FABP was higher in the AMI group compared with non-AMI group (P < .001). Body surface potential map STE was significantly associated with H-FABP elevation (P < .001). Of those with initial cTnT less than 0.03 μg/L, the c-statistic for the receiver operating characteristic curve distinguishing AMI from non-AMI using H-FABP alone was 0.644 (95% confidence interval [CI], 0.521-0.771), using BSPM alone was 0.716 (95% CI, 0.638-0.793), and using the combination of BSPM and H-FABP was 0.812 (95% CI, 0.747-0.876; P < .001).

CONCLUSION

In patients with acute ischemic-type chest pain who have a normal cTnT at presentation, the combination of H-FABP and BSPM at first assessment identifies those with early AMI (c-statistic, 0.812; P < .001), thus allowing earlier triage to reperfusion therapy and secondary prevention.

Heart-type fatty acid binding protein as an adjunct to cardiac troponin-I for the diagnosis of myocardial infarction

We hypothesized that when used in combination with cardiac troponins, heart-type fatty acid binding protein (H-FABP) would have greater diagnostic value than conventional markers for the early diagnosis of myocardial infarction (MI). Patients with typical chest pain at a single emergency department were consecutively enrolled. Initial blood samples were drawn for H-FABP, myoglobin, creatine kinase isoenzyme MB (CK-MB), and cardiac troponin-I (cTnI) measurements. MI was defined by serial cTnI measurements. To evaluate the adjunctive role of biochemical markers, we derived and compared logistic regression models predicting MI in terms of their discrimination (area under the receiver operating characteristics curve, AUC) and overall fit (Bayesian information criterion, BIC). Seventy-six of 170 patients were diagnosed as having MI. The AUC of cTnI, H-FABP, myoglobin, and CK-MB were 0.863, 0.827, 0.784, and 0.772, respectively. A logistic regression model using cTnI (P = 0.001) and H-FABP (P < 0.001) had the biggest AUC (0.900) and the best fit determined by BIC. Sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio of this model at 30% probability were 81.6%, 80.9%, 4.26, and 0.23, respectively. H-FABP has a better diagnostic value than both myoglobin and CK-MB as an adjunct to cTnI for the early diagnosis of MI.

The utility of troponin measurement to detect myocardial infarction: review of the current findings

Myocardial infarction (MI) is defined by the presence of myocardial necrosis in combination with clinical evidence of myocardial ischemia. Cardiac troponins are regulatory proteins within the myocardium that are released into the circulation when damage to the myocyte has occurred. Therefore, serum troponin is an exquisitely sensitive marker of myocardial injury and is necessary for establishing the diagnosis of MI. High-sensitivity troponin assays are improving the diagnostic accuracy and rapid detection of myocardial infarction. The early identification of MI is vital for the institution of anti-thrombotic therapy to limit myocardial damage and preserve cardiac function. Troponin has both diagnostic and prognostic significance in the setting of acute coronary syndrome (ACS). Increased troponin levels in the absence of ACS should prompt an evaluation for an alternative, non-thrombotic mechanism of troponin elevation and direct management at the underlying cause. This review describes the role of troponin in the evaluation of patients with suspected myocardial infarction.

Comparison of usefulness of heart-type fatty acid binding protein versus cardiac troponin T for diagnosis of acute myocardial infarction

We aimed to assess the additive diagnostic value of measuring the serum levels of soluble human heart-type fatty acid binding protein (H-FABP) in the early diagnosis of acute myocardial infarction (AMI) in unselected patients with chest pain. A total of 97 consecutive patients with acute ischemic-type chest pain were prospectively enrolled and classified according to the American Heart Association/American College of Cardiology guidelines. The test characteristics of H-FABP and cardiac troponin T serum levels at admission revealed a greater sensitivity of H-FABP in the first 4 hours of symptoms (86% vs 42%, p <0.05). Combining H-FABP and cardiac troponin T also improved the sensitivity in the detection of AMI (97% vs 71%, p <0.05) but demonstrated a greater misclassification rate (25% vs 9%, p <0.05). The specificity of H-FABP was poor (65%, 95% confidence interval 58% to 71%). Receiver operating characteristics revealed a poor performance of H-FABP in patients with non-ST-elevation myocardial infarction. Classification tree analysis demonstrated that an H-FABP-related improvement in the early definite rule-out of AMI (reduction of false-negative rate from 11% to 3%) was at the expense of an increase in the false-positive rate to 5%. In conclusion, measurement of H-FABP, in addition to cardiac troponin T, serum levels within the first 4 hours of symptoms improves the sensitivity and negative predictive value for the detection of AMI at the cost of test accuracy and precision, especially in patients with non-ST-elevation myocardial infarction.

Clinical usefulness of measuring red blood cell distribution width on admission in patients with acute coronary syndromes

BACKGROUND

Conventional cardiac markers used for the biochemical diagnosis of acute coronary syndromes (ACS) have a high specificity but low sensitivity within 2-4 h of symptoms onset. The red blood cell distribution width (RDW), reflecting the size variability of circulating red blood cells, has been shown to be independently associated with an increased risk of major cardiovascular events. We assessed whether there is an association between RDW at admission and cardiac troponin T (cTnT) elevation in patients with chest pain.

METHODS

We analyzed RDW values in 2304 adult patients, who were consecutively admitted over a 1-year period to the local emergency department for chest pain suggestive of ACS. In all patients, a baseline blood sample was collected for routine haematological testing, whereas cTnT was measured at baseline and after 4, 6, and 12 h.

RESULTS

A total of 456 patients (19.8% of total) had ACS. These patients, all having cTnT> or =0.03 microg/L up to 12 h from admission other than ischaemic electrocardiographic changes, had higher RDW than non-ACS patients [median 15.1%, (5th-95th percentiles) 13.2%-19.0% vs. 13.5%, 12.9%-17.1%, p<0.001]. On admission, the sensitivity and specificity of cTnT were 94% (25 false negative results) and 100%, respectively. The diagnostic accuracy of RDW, as calculated by the receiver operating characteristic curve analysis, was 0.705 (p<0.001). At the cut-off value of 14%, the clinical sensitivity and specificity of RDW on admission were 79% and 50%, respectively. In 21 out of 25 patients classified as false negative for cTnT on admission, the RDW was >14%. Accordingly, the diagnostic sensitivity of the two combined measurements on admission was 99%.

CONCLUSIONS

As RDW is widely available to clinicians as a part of the complete blood count, and therefore incurs no additional costs, it might be considered with other conventional cardiac markers for the risk stratification of ACS patients admitted to emergency departments.

Different collection tubes in cardiac biomarkers detection

The role played by different collection tubes is one of the more frequently forgotten parameters, which influences the quality of laboratory results.We aimed to determine whether there is a significant difference in assay of myoglobin, cardiac troponin I, and CK-MB depending on the presence of anticoagulant and gel separator in the collecting tubes.Blood samples were collected in 40 consecutive patients admitted for acute coronary syndrome. The samples were taken at the same moment in three different tubes (tubes without anticoagulant and with gel separator, heparin tubes with gel separator and heparin tubes without gelseparator;Venosafe, Terumo Europe, Leuven Belgium). Myoglobin, CK-MB and cardiac troponin I were measured with a double side (sandwich) chemiluminescent immuenzymatic assay (Access Myoglobin, Access CK-MB, Access AccuTnI).Cardiac troponin I was not influenced by the type of collection tube used. On the contrary, myoglobin and CK-MB showed a statistical difference depending on the test tube. In particular, there was a significant difference between tubes without anticoagulant and with gel separator and tubes with heparin and without gel.

Biomarkers in Acute Coronary Syndrome

BACKGROUND: Evaluation of patients who present to the hospital with acute undifferentiated chest pain or other symptoms and signs suggestive of Acute Coronary Syndrome (ACS) is often a clinical challenge. The initial assessment, requiring a focused history (including risk factors analysis), a physical examination, an electrocardiogram (EKG) and serum cardiac marker determination, is time-consuming and troublesome. Recent investigations have indicated that increases in biomarkers of necrosis, inflammation, ischemia and myocardial stretch may provide earlier assessment of overall patient risk, help in identifying the adequate diagnostic and therapeutic management for each patient and allow for prevention of substantial numbers of new events. APPROACH AND CONTENT: The purpose of this review is to provide an overview of the characteristics of several biomarkers that may have potential clinical utility to identify ACS patients. Patho-physiology, analytical and clinical characteristics have been evaluated for each marker, underlying the properties for potential routine clinical use. SUMMARY: The biomarkers discussed in this review are promising and might lead to improved diagnosis and risk stratification of patients with ACS, however their clinical application requires further studies. It is important to define their clinical role as diagnostic markers, their predictive value and the specificity, standardization and detection limits of the assays.

Management of acute coronary syndrome

This is a review of acute coronary syndrome as a clinical entity. An appreciation of acute coronary syndrome as a disease spectrum is presented along with contemporary evidence for its diagnosis and approach to medical and surgical management.

Influence of acute physical exercise on emerging muscular biomarkers

: Although there is comprehensive information on traditional biomarkers of muscle and cardiac damage following exercise, less is known on the kinetics of innovative markers, including ischemia modified albumin (IMA), glycogen phosphorylase isoenzyme BB (GPBB), carbonic anhydrase III (CAIII) and heart-type fatty acid-binding protein (H-FABP) in athletes performing a sub-maximal exercise.

: A total of 10 healthy trained Caucasian males performed a 21-km run. Blood samples were collected before the run, immediately after (post), 3, 6 and 24 h thereafter. Cardiac troponin I (cTnI), myoglobin, creatine kinase isoenzyme MB (CK-MB), GPBB, CAIII and H-FABP were assayed using a new diagnostic system based on protein biochip array technology. IMA was measured by a commercial colorimetric assay on a Roche Modular system P.

: Significant variations by one-way analysis of variance were observed for CK-MB (p=0.013), myoglobin (p<0.001), GPBB (p=0.029), H-FABP (p<0.001), CAIII (p=0.006), but not for cTnI (p=1.00) and IMA (p=0.881). In particular, values of all the biomarkers tested, but cTnI and IMA, increased significantly immediately after the run. GPBB and H-FABP values returned to baseline 6 and 3 h thereafter, those of CAIII, CK-MB and myoglobin remained significantly elevated from the pre-run value up to 24 h after the run. The major variation over pre-run values was recorded for myoglobin (nearly 4-fold increment), whereas CAIII, CK-MB, GPBB and H-FABP increased by 2.9-, 1.8-, 1.4- and 1.2-fold, respectively.

: We conclude that a sub-maximal aerobic exercise influences the concentration of several markers of muscle damage. Except for IMA, not one of the emerging biomarkers tested can be safely used to rule out myocardial damage as well as cardiospecific troponins in patients who had undergone recent physical activity.

Clin Chem Lab Med 2008;46:1313–8.

In vitro and in vivo examination of cardiac troponins as biochemical markers of drug-induced cardiotoxicity

Cardiac troponin T (cTnT) and troponin I (cTnI) are becoming acknowledged as useful biochemical markers of drug-induced cardiotoxicity. In this study we examined the release kinetics of cTnT and cTnI using an in vitro model of isolated rat neonatal ventricular cardiomyocytes (NVCM, 72h treatment with 0.1-3microM of daunorubicin) and compared it with data from a rabbit model of chronic anthracycline-induced cardiomyopathy in vivo (3mg/kg of daunorubicin weekly, 10 weeks). In cell-culture media, the cTnI and cTnT concentrations were concentration- and time-dependently increasing in response to daunorubicin exposure and were negatively exponentially related to cardiomyocyte viability. With 3microM daunorubicin, the relative increase of AUC of cTnT and cTnI was 2.4- and 5.3-fold higher than the increase of LDH activity, respectively. In rabbits, the daunorubicin-induced cardiomyopathy was associated with progressive increase of both cTnT and cTnI. Although the correlation between cTnT and cTnI cumulative release (AUCs) was found (R=0.81; P<0.01) and both cardiac troponins corresponded well with the echocardiographically-assessed systolic dysfunction (R=0.83 and 0.81 for cTnT and cTnI, respectively; P<0.001), the first significant increase in cTnI levels was observed earlier (at a cumulative daunorubicin dose of 200mg/m(2)) than with cTnT (350mg/m(2)). In conclusion, our study has confirmed cTnT and cTnI as very sensitive and specific markers of anthracycline-induced cardiotoxicity. The troponins can become not only the bridge between the clinical and experimental studies of drug-induced cardiotoxicity but also the linkage between the preclinical experiments in vitro and in vivo.

The exciting story of cardiac biomarkers: from retrospective detection to gold diagnostic standard for acute myocardial infarction and more

This paper reviews the history of the contribution of the laboratory medicine to clinical cardiology and discusses the most important steps in this field. Until 20 years ago, the clinical laboratory only placed at the cardiologist's disposal a few assays for the retrospective detection of cardiac tissue necrosis, such as enzymatic methods for creatine kinase and lactate dehydrogenase activities. However, in the latter part of the 20th century, highly sensitive and specific assays, such as cardiac troponins, as well as assays for markers of myocardial function, such as cardiac natriuretic peptides, rapidly changed the scenario of clinical management of patients with cardiac diseases, assigning to the laboratory a pivotal role in the overall diagnostic flow. This is witnessed by the recent incorporation of these markers into international guidelines and in the redefinition of myocardial infarction. For the foreseeable future, new serum markers of myocardial ischemic, i.e. reversible, injury or related to coronary plaque instability and disruption are expected.

The sensitivity of cardiac markers stratified by symptom duration

We compared the sensitivity of three commonly used cardiac markers between two subpopulations, those who came to the Emergency Department (ED) late (6-24 h) after their symptoms began, and those who arrived earlier (<6 h), in a prospective comparative trial. Among all adult patients who presented to our ED with symptoms suggestive of acute myocardial infarction (MI), we drew serum for myoglobin, CK-MB, and troponin I upon arrival (time 0) and 2 h later. Outcomes, including acute MI, were determined. Sensitivities for all three markers between the subpopulations who arrived fewer than 6 h from symptom onset were compared to those who arrived later (6-24 h). We enrolled 346 eligible subjects, 36% of whom described cardiac symptoms as beginning 6 or more hours earlier; 14% suffered acute MIs. For time 0, the sensitivity of all three markers for acute MI was significantly higher among those subjects with symptoms of 6 or more hours' duration as compared to those with less. For troponin I, the increase in sensitivity between these two subpopulations approached 300%. At the time of the 2-h sample, the differences in sensitivities were much less and were not statistically significant. We conclude that cardiac marker values obtained at time 0 among Emergency Department patients who arrive 6 or more hours after cardiac symptom onset provide significantly higher sensitivities as compared to those obtained in patients who arrive earlier. For troponin I, the increase in sensitivity approaches threefold.

Serum deoxyribonuclease I activity can be used as a sensitive marker for detection of transient myocardial ischaemia induced by percutaneous coronary intervention

AIMS

Cardiac markers such as troponin T (c-TnT) have proven unsuitable for the detection of early and transient myocardial ischaemia. We recently reported that abrupt elevation of serum deoxyribonuclease I (DNase I) activity in the early stage of acute myocardial infarction could be used as a diagnostic marker. To evaluate whether serum DNase I could be used as a marker of early myocardial ischaemia, we investigated alterations in its levels after transient ischaemia induced during percutaneous coronary intervention (PCI).

METHODS AND RESULTS

In 24 consecutive patients with stable angina undergoing elective PCI and 12 patients undergoing coronary angiography (CAG), serum samples were tested for DNase I, creatine kinase isoenzyme MB (CK-MB), and c-TnT before, soon after, and 3 and 12-24 h after completion of the procedures. Serum DNase I activity had risen significantly from baseline by 3 h after PCI in 21 of the 24 PCI patients. The mean per cent difference from baseline in serum DNase I activity 3 h after PCI was 35.9+/-37.5%. Even among the 16 PCI patients whose levels of CK-MB and c-TnT were within the normal range, 13 showed elevation of serum DNase I activity from baseline after PCI. In the CAG patient group, DNase I activity levels remained unchanged at all times after CAG.

CONCLUSION

Elevation of serum DNase I activity can be used as a sensitive marker for detection of transient myocardial ischaemia.

Monitoring of cardiac function on the basis of serum troponin I levels in patients with acute leukemia treated with anthracyclines

Anthracyclines are used extensively in the therapy of hematologic malignancies. However, their use has been limited by acute and chronic cardiotoxicity. Cardiac troponins have emerged as sensitive and specific markers of even minor myocardial damage. In this study we prospectively evaluated serial measurements of serum cardiac markers and echocardiography in patients with de novo acute myeloid and lymphoid leukemias (AML and ALL, respectively) treated with anthracyclines. We examined and subdivided 79 patients into 3 groups: group 1 (37 patients with AML, all < 60 years), group 2 (25 with AML, all 260 years), group 3 (17 with ALL). Serum specimens were collected before treatment and during and after therapy and were analyzed for troponin I (Tnl), myoglobin, creatine phosphokinase-muscle myocardium isoenzyme B, and lactate dehydrogenase concentrations. In group 1, 4 of the 37 patients (11%) had increased levels of Tnl on the 14th day of induction therapy, but by the 28th day the Tnl level had returned to normal in 3 of these 4 patients. In group 2, 3 of the 25 patients (12%) demonstrated increased Tnl concentrations on the 7th day of induction therapy, but by the 14th day these levels had normalized in 2 of the 3. In group 3, we detected no increased Tnl concentrations. Echographic study did show a significant correlation with the Tnl levels (P < .001), involving a reversible decrease in left ventricular ejection fraction among patients with increased Tnl levels (> 0.15 ng/mL) on day 14 in group 1 and on day 7 in group 2. These results may aid the clinician in the treatment of patients by identifying high-risk patients who may benefit from closer observation or supportive cardiac therapy.

Delta creatine kinase–MB outperforms myoglobin at two hours during the emergency department identification and exclusion of troponin positive non–ST-segment elevation acute coronary syndromes

STUDY OBJECTIVE

Limited information is available about the diagnostic performance of creatine kinase (CK)-MB and myoglobin levels during the early evaluation of chest pain patients using cardiac troponins as the criterion standard for diagnosing acute myocardial infarction. In this study, we compare the sensitivity and specificity of the baseline, 2-hour absolute, and 2-hour delta values of myoglobin and CK-MB mass assay for detection of acute myocardial infarction using cardiac troponin I (troponin) as the sole marker of myocardial necrosis.

METHODS

A prospective observational study was conducted of 975 chest pain patients with a baseline troponin level of 1.0 ng/mL or less (Abbott Axsym Assay) and an initial ECG nondiagnostic for injury. CK-MB, myoglobin, and troponin levels were all measured on the Abbott Axsym immunoassay. Acute myocardial infarction was diagnosed if there was at least 20 minutes of chest pain and any one of the following criteria within 24 hours of ED presentation: a serial increase in troponin to more than 1.0 ng/mL, new Q-wave formation in 2 contiguous leads, or patient death by cardiac or unknown cause. The optimal values of CK-MB and myoglobin were chosen at the most accurate value on the receiver operating characteristic (ROC) curve (ie, value with lowest false-negative and false-positive rate) of the 2-hour absolute and 2-hour delta value for predicting acute myocardial infarction.

RESULTS

Acute myocardial infarction was diagnosed in 44 (4.5%) of the 975 study patients. ROC curve analysis revealed no statistically significant differences in areas for myoglobin and CK-MB values at baseline and 2 hours for determination of acute myocardial infarction. However, the ROC curve area of the delta CK-MB level significantly outperformed the ROC curve area of the delta myoglobin level for early identification of acute myocardial infarction (0.97 versus 0.81; 95% confidence interval [CI] for difference between areas 0.09 to 0.24). At the most accurate cutoff value, a 2-hour delta CK-MB level more than 0.7 ng/mL had a sensitivity of 93.2% (95% CI 81.3% to 98.5%), a specificity of 94.4% (95% CI 92.7% to 95.8%), a positive likelihood ratio of 16.7, and a negative likelihood ratio of 0.07.

CONCLUSION

A 2-hour delta CK-MB level outperforms myoglobin level in the early identification and exclusion of acute myocardial infarction in non-ST-segment elevation chest pain patients. This finding suggests that myoglobin may no longer be the optimal early marker of acute myocardial infarction when troponins are used as the criterion standard.

Clinical significance of cardiac troponin T levels in chronic kidney disease patients: predictive value for cardiovascular risk

BACKGROUND

Recent studies have shown that cardiac troponin T (cTnT) levels predict cardiovascular mortality in hemodialysis patients. The aim of this study is to analyze the prognostic value of cTnT levels in stable patients with moderate chronic kidney disease (CKD).

METHODS

One hundred seventy-six outpatients were included; 128 patients had an estimated glomerular filtration rate (GFR) less than 60 mL/min (<1 mL/s; CKD group), and 48 patients, 60 mL/min or greater (> or =1 mL/s; control group). Medical records for cardiovascular factors were recorded. Analytical parameters and cardiac markers were analyzed. Patients were followed up prospectively, and the end points were fatal and nonfatal cardiovascular events.

RESULTS

cTnT levels were undetectable in all control group patients (cTnT < 0.01 ng/mL), and only 20 patients in the CKD group had detectable values (>0.01 ng/mL). Patients with detectable cTnT levels were older (P = 0.005), had a greater prevalence of congestive heart failure (CHF; P = 0.000) and left ventricular hypertrophy (P = 0.001), more anemia (P = 0.008), and a lower GFR (P = 0.008) than the rest of the patients in the CKD group. After a mean follow-up of 12.9 months, 20 patients in the CKD group and 1 patient in the control group experienced a cardiovascular event. Age (odds ratio [OR], 1.11), previous coronary artery disease (OR, 2.49), CHF (OR, 7.36), hemoglobin level (OR, 0.70), GFR (OR, 0.94), pulse pressure (OR, 1.02), and cTnT level (OR, 12.34) predicted cardiovascular events on univariate Cox analysis.

CONCLUSION

In patients with CKD, cTnT level is a predictor of cardiovascular events.

Standardization of immunoassays for measurement of myoglobin in serum. Phase I: Evaluation of candidate secondary reference materials

BACKGROUND

Myoglobin is a low-molecular weight protein present in the cytosol of striated muscles. Its concentrations in serum can be measured by immunoassays and are used as an early indicator of myocardial necrosis. Since variability among commercial myoglobin assays exists, standardization of myoglobin assays is needed.

METHODS

An international collaborative study was organized with the involvement of seven companies using 12 different automated platforms for measuring myoglobin. Five candidate secondary, i.e., matrixed, reference materials were assayed in relation to linearity, imprecision, recovery rate and commutability to demonstrate a possible identity between the materials and the usual routine serum samples.

RESULTS

One lyophilized candidate material (human heart myoglobin in human serum) was selected as the most suitable secondary reference material, based on the criteria examined. Used as a calibrator a posteriori, the bias between the various myoglobin assays for a frozen human serum pool was reduced from 32% to 13%.

CONCLUSION

This study provides the basis for the selection of an internationally recognized secondary reference material.

Current concepts in standardization of cardiac marker immunoassays

Cardiac markers are measured by a number of different immunoassays using specific antibodies directed to the respective antigens. Lacking assay standardization, different results from different assays measuring the same marker may be obtained and this problem may cloud interpretations of reported data. Presently, there are no reference procedures for cardiac markers; certified reference materials should still be established and, at least for cardiac troponins, the analyte in the patients' blood is significantly different from newly synthesized protein. It is therefore clear that the problems of cardiac marker standardization will not be quickly solved. A number of projects are, however, underway under the auspices of the IFCC and other organizations. The aim of this opinion is to reflect on some concepts related to the implementation of a metrologically correct measurement system, giving practical examples on how these concepts can be applied to immunoassays measuring cardiac markers.

Biochemical markers of cardiac diseases

This article reviews the current contribution of the determination of biochemical markers to clinical cardiology and discusses some important developments in this field. Biochemical markers play a pivotal role in the diagnosis and management of patients with acute coronary syndrome (ACS), as witnessed by the incorporation of cardiac troponins into new international guidelines for patients with ACS and in the redefinition of myocardial infarction. Despite the success of cardiac troponins, there is still a need for development of early markers that can reliably rule out ACS from the emergency room at presentation and detect myocardial ischemia also in the absence of irreversible myocyte injury. Under investigation are two classes of indicators: markers of early injury/ischemia and markers of coronary plaque instability and disruption. Finally, with the characterization of the cardiac natriuretic peptides, Laboratory Medicine is also assuming part in the assessment of cardiac function.

Evidence-based laboratory medicine as a tool for continuous professional improvement

BACKGROUND

Evidence-based medicine (EBM), defined as "the conscientious, explicit, and judicious use of the current best evidence in making decisions about the care of patients," seems a tool (a "new paradigm") able to meet individual clinical experience with robust observations. EBM has been driven by the need to manage information overload by cost control and by public request for the best in diagnostics and treatment.

METHODS

The application of EBM in laboratory medicine or evidence-based laboratory medicine (EBLM) is aimed to advance clinical diagnosis by researching and disseminating new knowledge, combining methods from clinical epidemiology, statistics, and social science with the traditional pathophysiological molecular approach.

RESULTS

EBLM, by evaluating the role of diagnostic investigations in the clinical decision-making process with emphasis on measurable outcome, can help both in improving the quality of new scientific findings and in translating the results of good-quality research into everyday practice.

CONCLUSIONS

Since there is a need to integrate many educational tools to focus the strategy on promoting the implementation of best practices, the STARD proposal for robust diagnostic test primary studies, the presence of systematic reviews of high quality, and the development of valid guidelines based on the best scientific evidence may be useful to promote an a evidence-based culture for appropriateness, efficiency, and effectiveness in laboratory medicine.

The diagnostic value of troponin T and myoglobin levels in acute myocardial infarction: a study in Turkish patients

This study compares the diagnostic value of troponin T (TnT) and myoglobin with creatinine kinase (CK) for myocardial infarction (MI) in a tertiary care centre in a developing nation. The study group comprised 33 acute myocardial infarction patients and 27 healthy controls. Receiver operating characteristic curves for TnT, myoglobin and CK were drawn and areas under the curve calculated. At admission, myoglobin levels had greater diagnostic sensitivity than TnT or CK levels. After 2 h, myoglobin and TnT had equal sensitivity and specificity, whereas CK still had lower sensitivity than myoglobin and TnT. After 4 h there was no difference between the tests. It was concluded that myoglobin levels on admission and TnT at 2 h had the greatest diagnostic rate, whereas all the tests were similar after 4 h for MI.

Acute coronary syndrome: biochemical strategies in the troponin era

New biomarkers, such as cardiac troponins, have a major role to play for cost-effective management of individuals with acute chest pain and suspected coronary syndrome, and the laboratory is now poised to assume a vital role in assessing damage and determining prognosis. The redefined biochemical criterion proposed to classify acute coronary syndrome patients presenting with ischemic symptoms as patients with myocardial infarction is heavily predicated on an increased troponin concentration in blood. In an era of evidence-based medicine, we can no longer overlook the diagnostic and prognostic benefits provided by the measurement of these highly sensitive and specific proteins.

Coronary angiographic findings in patients with clinical unstable angina according to cardiac troponin I and T concentrations in serum

CONTEXT

Elevated cardiac troponin levels have been reported to identify unstable angina patients at high risk.

OBJECTIVE

To examine the relation of cardiac troponin I (cTnI) and cardiac troponin T (cTnT) levels to findings of coronary angiography in these patients.

METHODS

Samples for troponin estimation were taken every 4 hours throughout the first 48 hours after admission before angiography in 34 patients with primary unstable angina. Patients were considered to be troponin positive if the marker was increased (>0.04 microg/L for cTnT and >0.03 microg/L for cTnI) in at least one sample collected.

RESULTS

An increased troponin (I or T) concentration was documented in 14 patients (41.2%). Twelve patients (35.3%) had elevations of both markers, whereas the remaining 2 patients had elevations of cTnI or cTnT alone. Patients with or without increased troponin levels did not differ with respect to degree of coronary disease at angiography. However, patients with elevated troponin concentrations had more complex lesion characteristics. In 69% of patients with increased cTnI levels and in 77% of patients with increased cTnT levels, type B2 or C lesions were documented with presence of ulcerated plaques and thrombus formation. In contrast, only 23% of the patients with elevated cTnI or cTnT levels had type A lesions compared with 71% of patients with negative troponin concentrations.

CONCLUSIONS

Patients with unstable angina who have significant release of cTnI and/or cTnT have evidence of more complex lesions on coronary angiography, supporting the hypothesis that both troponins might be used without distinction as surrogate markers for microembolization from thrombus formation on a disrupted plaque.

Comparative study of cardiac troponin I and T measurements in a routine extra-cardiological clinical setting

This study compared troponin I (cTnI) to troponin T (cTnT) in a population admitted to General Medicine Divisions in whom acute myocardial infarction (AMI) was suspected; 98 consecutive patients were included. Diagnoses were made without knowledge of troponin results: 51 patients had AMI, and 47 (including 8 with unstable angina) had no AMI. Patients were considered to be troponin positive if the marker concentration was >99th percentile value of the reference population. Both troponins were associated with an almost absolute sensitivity for AMI (100% for cTnI and 98.0% for cTnT), while the specificity was marginally higher for cTnI (78.7% vs. 68.1%). Increased cTnI and/or cTnT were observed in 15 patients out of 39 without acute coronary syndromes. Simultaneous positivity was seen in 8 patients with severe disorders and complications. Discordances were more frequent in favor of increased cTnT (n = 5) than the opposite (n = 2), even if this difference did not achieve statistical significance. cTnI and cTnT detected AMI with comparable efficiency. Cases without coronary syndrome positively concordant for troponins confirmed the ability of these biomarkers to detect myocardial injury undetectable by conventional diagnostic approaches.

Present issues in the determination of troponins and other markers of cardiac damage

OBJECTIVE

To review some of the recently proposed improvements and the corresponding apparent issues in the field of biochemical markers of cardiac damage.

CONCLUSIONS

The continuous development of new analytical tools for the biochemical evaluation of patients with suspected myocardial injury brings without doubt new challenges of careful technological evaluation, implementation, and standardization but it may also provide a unique opportunity to markedly enhance our diagnostic performance in the clinical setting of acute coronary syndrome.