Cardiac biomarkers - A short biography

Prevalence of stable coronary artery disease and its associated clinical factors among patients with chest pain and elevated cardiac troponin alone

Cardiac troponin is a useful test for diagnosing cardiogenic causes in patients with chest pain. However, cardiac troponin levels are often elevated in patients with chest pain due to non-cardiac causes other than coronary artery disease. The purpose of this study was to investigate the prevalence of coronary artery disease (CAD) and its associated factors in patients with chest pain and elevated cardiac troponin I (cTnI). 104 patients (mean age, 65 ± 11 years; 60 [58%] men) who underwent coronary angiography (CAG) for chest pain and elevated cTnI levels were enrolled in this study. All patients had a normal CK-MB range and did not show any ischemic changes on electrocardiography or echocardiography. Patients were classified into two groups according to the presence of CAD (Group 1, n = 62) and the absence of CAD (Group 2, n = 42). Patients were classified into subgroups according to the presence (Group 2a, microvascular angina [MVA], n = 18) and absence (Group 2b, non-angina [NA], n = 25) of angina. CAD was diagnosed in 62 (60%) patients and MVA was suspected in 18 (17%) patients without CAD. Patients with CAD showed elevated blood pressure and slightly decreased heart rate. Diabetes mellitus was more prevalent in patients with CAD and patients without CAD (esp. with MVA) were more likely to be common drinkers. Increased relative wall thickness (RWT) and reduced E' velocity were associated with CAD. High-density lipoprotein (HDL) levels were reduced in patients with CAD and MVA but were higher in patients with NA. Lower HDL level was found to be independently associated with the presence of CAD. Elevated cTn1 levels without other evidence of myocardial ischemia are sufficient for performing CAG in patients with stable chest pain.

Cardiovascular Biomarkers: Lessons of the Past and Prospects for the Future

Cardiovascular diseases (CVDs) are a major healthcare burden on the population worldwide. Early detection of this disease is important in prevention and treatment to minimise morbidity and mortality. Biomarkers are a critical tool to either diagnose, screen, or provide prognostic information for pathological conditions. This review discusses the historical cardiac biomarkers used to detect these conditions, discussing their application and their limitations. Identification of new biomarkers have since replaced these and are now in use in routine clinical practice, but still do not detect all disease. Future cardiac biomarkers are showing promise in early studies, but further studies are required to show their value in improving detection of CVD above the current biomarkers. Additionally, the analytical platforms that would allow them to be adopted in healthcare are yet to be established. There is also the need to identify whether these biomarkers can be used for diagnostic, prognostic, or screening purposes, which will impact their implementation in routine clinical practice.

Development of A Lateral Flow Highway: Ultra-Rapid Multitracking Immunosensor for Cardiac Markers

The integration of several controlled parameters within a single test system is experiencing increased demand. However, multiplexed test systems typically require complex manufacturing. Here, we describe a multiplexed immunochromatographic assay that incorporates a conventional nitrocellulose membrane, which is used together with microspot printing, to construct adjacent microfluidic "tracks" for multiplexed detection. The 1 mm distance between tracks allows for the detection of up to four different analytes. The following reagents are applied in separate zones: (a) gold nanoparticle conjugates with antibodies against each analyte, (b) other antibodies against each analyte, and (c) antispecies antibodies. The immersion of the test strip in the sample initiates the lateral flow, during which reagents of different specificities move along their tracks without track erosion or reagent mixing. An essential advantage of the proposed assay is its extreme rapidity (1-1.5 min compared with 10 min for common test strips). This assay format was applied to the detection of cardiac and inflammatory markers (myoglobin, D-dimer, and C-reactive protein) in human blood, and was characterized by high reproducibility (8%-15% coefficient of variation) with stored working ranges of conventional tests. The universal character of the proposed approach will facilitate its use for various analytes.

Troponins, Acute Coronary Syndrome and Renal Disease: From Acute Kidney Injury Through End-stage Kidney Disease

The diagnosis of acute coronary syndromes (ACS) is heavily dependent on cardiac biomarker assays, particularly cardiac troponins. ACS, particularly non-ST segment elevation MI, are more common in patients with acute kidney injury, chronic kidney disease (CKD) and end-stage kidney disease (ESKD), are associated with worse outcomes than in patients without kidney disease and are often difficult to diagnose and treat. Hence, early accurate diagnosis of ACS in kidney disease patients is important using easily available tools, such as cardiac troponins. However, the diagnostic reliability of cardiac troponins has been suboptimal in patients with kidney disease due to possible decreased clearance of troponin with acute and chronic kidney impairment and low levels of troponin secretion due to concomitant cardiac muscle injury related to left ventricular hypertrophy, inflammation and fibrosis. This article reviews the metabolism and utility of cardiac biomarkers in patients with acute and chronic kidney diseases. Cardiac troponins are small peptides that accumulate in both acute and chronic kidney diseases due to impaired excretion. Hence, troponin concentrations rise and fall with acute kidney injury and its recovery, limiting their use in the diagnosis of ACS. Troponin concentrations are chronically elevated in CKD and ESKD, are associated with poor prognosis and decrease the sensitivity and specificity for diagnosis of ACS. Yet, the evidence indicates that the use of high-sensitivity troponins can confirm or exclude a diagnosis of ACS in the emergency room in a significant proportion of kidney disease patients; those patients in whom the results are equivocal may need longer in-hospital assessment.

Procalcitonin: Where Are We Now?

Procalcitonin is a biomarker that is generally elevated in bacterial infections. This review describes a conceptual framework for biomarkers using lessons from the history of troponin, applies this framework to procalcitonin with a review of observational studies and randomized trials in and out of the intensive care unit, and concludes with clinical recommendations and thoughts on how to test a test.

Cardiac troponins: from myocardial infarction to chronic disease

Elucidation of the physiologically distinct subunits of troponin in 1973 greatly facilitated our understanding of cardiac contraction. Although troponins are expressed in both skeletal and cardiac muscle, there are isoforms of troponin I/T expressed selectively in the heart. By exploiting cardiac-restricted epitopes within these proteins, one of the most successful diagnostic tests to date has been developed: cardiac troponin (cTn) assays. For the past decade, cTn has been regarded as the gold-standard marker for acute myocardial necrosis: the pathological hallmark of acute myocardial infarction (AMI). Whilst cTn is the cornerstone for ruling-out AMI in patients presenting with a suspected acute coronary syndrome (ACS), elevated cTn is frequently observed in those without clinical signs indicative of AMI, often reflecting myocardial injury of 'unknown origin'. cTn is commonly elevated in acute non-ACS conditions, as well as in chronic diseases. It is unclear why these elevations occur; yet they cannot be ignored as cTn levels in chronically unwell patients are directly correlated to prognosis. Paradoxically, improvements in assay sensitivity have meant more differential diagnoses have to be considered due to decreased specificity, since cTn is now more easily detected in these non-ACS conditions. It is important to be aware cTn is highly specific for myocardial injury, which could be attributable to a myriad of underlying causes, emphasizing the notion that cTn is an organ-specific, not disease-specific biomarker. Furthermore, the ability to detect increased cTn using high-sensitivity assays following extreme exercise is disconcerting. It has been suggested troponin release can occur without cardiomyocyte necrosis, contradicting conventional dogma, emphasizing a need to understand the mechanisms of such release. This review discusses basic troponin biology, the physiology behind its detection in serum, its use in the diagnosis of AMI, and some key concepts and experimental evidence as to why cTn can be elevated in chronic diseases.

High-Sensitivity Troponin as a Biomarker in Heart Rhythm Disease

Biomarkers are important prognostic tools in various cardiovascular conditions, including coronary artery disease and heart failure. Although their utility in cardiac electrophysiology (EP) is less established, biomarkers may guide EP clinical practice by identifying patients at risk for developing arrhythmias and their complications, in addition to augmenting therapeutic decisions by targeting appropriate pharmacologic and interventional therapies to patients who may benefit most. In this review, we focus on the prognostic role of high-sensitivity cardiac troponin (hs-cTn) assays-which detect subclinical cardiac myocyte damage-in cardiac arrhythmias and their sequelae. We review the current literature on hs-cTn and its impact on various arrhythmia disease states and also provide suggestions for future research in this field. In conclusion, although the utility of hs-cTn assays remains at an investigational stage in cardiac EP, studies to date have suggested value as a prognostic biomarker in atrial fibrillation and as a screening marker for patients at high risk of sudden cardiac death (both in the general population and among those with hypertrophic cardiomyopathy).

How Well Do Laboratories Adhere to Recommended Clinical Guidelines for the Management of Myocardial Infarction: The CARdiac MArker Guidelines Uptake in Europe Study (CARMAGUE)

BACKGROUND

We undertook an assessment of current use of evidence-based guidelines for the use of cardiac biomarkers in Europe (EU) and North America (NA).

METHODS

In 2013–2014 a web-based questionnaire was distributed via NA and EU biochemical societies. Questions covered cardiac biomarkers measured, analytical methods used, decision thresholds, and use of decision-making protocols. Results were collated using a central database and analyzed using comparative and descriptive nonparametric statistics.

RESULTS

In EU, returns were obtained from 442 hospitals, 50% central or university hospitals, and 39% from local hospitals from 35 countries with 395/442 (89%) provided an acute service. In NA there were 91 responses (63.7% central or university hospitals, 19.8% community hospitals) with 76/91 (83.5%) providing an acute service. Cardiac troponin was the preferred cardiac biomarker in 99.5% (EU) and 98.7% (NA), and the first line marker in 97.7% (EU) and 97.4% (NA). There were important differences in the choice of decision limits and their derivations. The origin of the information was also significantly different, with EU vs NA as follows: package insert, 61.9% vs 40%; publications, 17.1% vs 15.0%; local clinical or analytical validation choice, 21.0% vs 45.0%; P = 0.0003.

CONCLUSIONS

There are significant differences between EU and NA use of cardiac biomarkers. This probably relates to different availability of assays between EU and NA (such as high-sensitivity troponin assays) and different laboratory practices on assay introduction (greater local evaluation of assay performance occurred in NA).

Point-of-care diagnostics for niche applications

Point-of-care or point-of-use diagnostics are analytical devices that provide clinically relevant information without the need for a core clinical laboratory. In this review we define point-of-care diagnostics as portable versions of assays performed in a traditional clinical chemistry laboratory. This review discusses five areas relevant to human and animal health where increased attention could produce significant impact: veterinary medicine, space travel, sports medicine, emergency medicine, and operating room efficiency. For each of these areas, clinical need, available commercial products, and ongoing research into new devices are highlighted.