High-Sensitivity Assays for Troponin in Patients with Cardiac Disease !

Troponin is a widely used biomarker in patients with cardiac disease. The use of troponin is well established in patients with suspected acute myocardial infarction (AMI), but troponin measurement is also used in other acute and nonacute settings. In patients with suspected AMI, early decision-making is crucial to allow rapid treatment and further diagnostic evaluation. Current guidelines recommend serial measurements of troponin with a cut-off concentration at the 99th percentile to triage patients in the emergency department.

Newer, high-sensitivity assays for troponin enable the detection of distinctly lower concentrations. Using these assays and very low cut-off concentrations, several rapid diagnostic strategies have been reported to improve diagnosis in acute cardiac care. Furthermore, noncoronary and non-acute applications of troponin assays — for example as a biomarker in patients with heart failure, pulmonary embolism, or stable coronary artery disease — are on the horizon and might improve individual risk stratification.

In this Review, we provide an overview on the development of high-sensitivity assays for troponin, and their application in patients with cardiac disease.

Pathophysiological background of troponin and troponin release

in different settings. A schematic overview of myocardial structure

related to troponin (inset), as well as the plasma troponin concentrations 

in different clinical settings (young and healthy, elderly or chronic diseases,

myocardial injury, and myocardial infarction).

Read more: High-Sensitivity Assays for Troponin in Patients with Cardiac Disease !

Source: NatureReviewsCadiology

Download in PDF

The Growing Impact of Cardiac Biomarkers in Clinical Chemistry.

Clinical chemistry measurements and calculations take into account an expansive set of analytes that reflect cardiac, liver, kidney, and other biological functions. Several of these discrete analytes are considered biomarkers, defined by Strimbu and Tavel as “a broad subcategory of medical signs [that are] objective indications of medical state observed from outside the patient which can be measured accurately and reproducibly.” In the case of cardiac biomarkers, the most common analytes are creatine kinase (CK), lactate dehydrogenase (LDH), and troponin (TNI). There are pros and cons to using these common chemistry tests as definitive cardiac biomarkers. However, other chemistry analytes and even some non-laboratory tests have been identified as potential cardiac biomarkers. Providing clinicians with accurate and thorough testing is important in contributing to diagnosis and ultimately to positive patient outcomes.

Read more: The Growing Impact of Cardiac Biomarkers in Clinical Chemistry.

Source: MedicalLaboratoryObserver

Heart Transplantation Recipients Unaffected by Donor Troponin Levels

Many transplant centers routinely reject hearts if the donor’s blood test reveals elevated levels of troponin I, a protein found in heart muscle that enters the bloodstream when there is a heart attack or other heart muscle damage. Donors with previous heart disease are automatically excluded.

Heart transplantation is one of the greatest achievements in modern medicine and patients with advanced heart failure in whom survival is measured in weeks and months are offered the potential for survival of equal to or greater than 10 years with excellent quality of life.

Read more: Heart Transplantation Recipients Unaffected by Donor Troponin Levels

According to new research, a blood test that leads to donor hearts being rejected may not effectively
predict whether a heart transplant will succeed or fail (Photo courtesy of the AMA).

Source: labmedica

High troponin levels may account for mental stress ischemia in cardiac patients.

Some people with heart disease experience a restriction of blood flow to the heart in response to psychological stress. Usually silent (not painful), the temporary restriction in blood flow, called ischemia, is an indicator of greater mortality risk.

Cardiologists at Emory University School of Medicine have discovered that people in this group tend to have higher levels of troponin -- a protein whose presence in the blood that is a sign of recent damage to the heart muscle-- all the time, independently of whether they are experiencing stress or chest pain at that moment.

The results are scheduled for presentation by cardiology research fellow Muhammad Hammadah, MD at the American College of Cardiology meeting in Chicago on April 3, as part of the Young Investigator Awards competition. Hammadah works with Arshed Quyyumi, MD, and Viola Vaccarino, MD, PhD, and colleagues at the Emory Clinical Cardiovascular Research Institute.

"Elevated troponin levels in patients with coronary artery disease may be a sign that they are experiencing repeated ischemic events in everyday life, with either psychological or physical triggers," Hammadah says.

Video source: High troponin levels may account for mental stress ischemia in cardiac patients.

Sourse: newsmedia.tasnimnews

Troponins as cardiac injury markers

Cardiac injury occurs when there is disruption of normal cardiac myocyte membrane integrity. This results in the loss into the extracellular space (including blood) of intracellular constituents including detectable levels of a variety of biologically active cytosolic and structural proteins, referred to as biomarkers, such as troponin, creatine kinase, myoglobin, heart-type fatty acid binding protein, and lactate dehydrogenase. Injury is usually considered irreversible (cell death), but definitive proof that cell death is an inevitable consequence of the process is not available. 

When a sufficient number of myocytes have died (myocyte necrosis) or lost function, acute clinical disease is apparent. Ischemia, with or without infarction, consequent to an imbalance between the supply and demand of oxygen (and nutrients) is the most common cause of cardiac injury. Other causes include trauma, toxins, and viral infection.

The biochemical characteristics and utility of troponins, the diagnosis of cardiac injury, and acute myocardial infarction (MI) in particular will be reviewed here. The other biomarkers of cardiac injury and disease states, other than an acute MI, in which elevation of biomarkers are seen are discussed separately.

Read more: Troponins as cardiac injury markers

Source: sciencsnutshell

Clinical Considerations for High-Sensitivity Cardiac Troponin Assays.

Cardiac troponins (cTn) have been available for nearly 2 decades in clinical laboratories and are now considered the gold standard for biochemical detection of myocardial infarction (MI). Furthermore, multiple organizations have endorsed the biomarkers’ use in both clinical and analytical guidelines. Today, the universal definition of MI includes the typical rise and/or fall of cTn with at least one value above the 99th percentile of a healthy reference population accompanied by at least one of the following clinical factors: presence of ischemic symptoms; electrocardiographic changes; or imaging evidence of loss of viable myocardium or a new wall motion abnormality.

However, a growing body of evidence now suggests that very low cTn values are clinically important. Investigators have found that patients who have cTn elevations considered normal, but near the 99th percentile, have worse prognoses and require more aggressive clinical management. These findings have prompted the search for newer techniques to enhance precision and enable measurements of cTn at or even below the 99th percentile cutoff.

Recently, researchers and commercial manufacturers have developed several high-sensitivity assays for cardiac troponin (hs-cTn) that are expected to be available soon for routine clinical use in the U.S. Understanding their analytical and clinical performance will be extremely important because under the current MI definition, a significant proportion of the general population would have evidence of myocardial injury. In this article, we will review the basic analytical and clinical characteristics of hs-cTn assays that are important for laboratory professionals to understand and describe how best to help clinicians employ these powerful assays.

Read more:
Clinical Considerations for High-Sensitivity Cardiac Troponin Assays.

Source: aacc, shutterstock