Point-of-care testing

The right diagnosis at the right time

The increasing use of high-sensitivity cardiac troponin testing is helping heart attack patients get the care they need more quickly while also reducing pressure on emergency departments.

Sameh Fahmy
Published on September 28, 2021

In many cases, the chest pain, shortness of breath and nausea strike suddenly and dramatically. Other times, patients experience a milder feeling of pressure or fullness in the chest that comes and goes. 

<p>Symptoms of a myocardial infarction, better known as a heart attack, can vary among individuals and even by gender, but they always necessitate a trip to the emergency department. In the United States alone, chest pain results in eight million annual visits to the emergency department. Yet only 5% of these visits result in a diagnosis of an acute coronary syndrome.[1] Differentiating chest pain caused by a heart attack from one caused by stable angina, anxiety, gastroesophageal pain, musculoskeletal pain or a range of other causes is notoriously difficult.</p>
Causes of chest pain
“We have a huge challenge with patients who have suspected acute coronary syndrome because we know the symptoms can be very atypical and unusual,” says Rick Body, MB, Professor of Emergency Medicine at the University of Manchester in the United Kingdom and Honorary Consultant in Emergency Medicine at Manchester University NHS Foundation Trust.[2]
<p>Fortunately, the increasing use of high-sensitivity testing for a biomarker known as <a href="cardiac troponin">cardiac troponin</a> I is helping patients get the care they need faster while also relieving pressure on emergency departments.</p>
These cardiac proteins are released in response to injury and can help diagnose acute myocardial infarction (AMI). High-sensitivity troponin I tests detect small changes to a patient’s troponin levels, which may be an early indication of AMI.
An electrocardiogram (ECG) is commonly used to evaluate patients who are experiencing chest pain, but only a minority of patients who present to the emergency department with chest pain have diagnostic ECG changes. Importantly, a normal electrocardiogram does not rule out acute coronary syndrome. One study found that approximately one third of patients overall and half of those admitted had a clinical diagnosis of an acute coronary syndrome without clear ECG changes.[3]
<p>Cardiac troponins are proteins that are found in the heart and are released into the bloodstream in response to injury. For decades, physicians have relied on the measurement of cardiac troponin (cTn) levels to help diagnose heart attacks.[4] In recent years, the advent of high-sensitivity tests that are able to detect substantially lower levels of cTn and smaller changes to a patient’s cTn levels have enabled physicians to more quickly identify and treat patients who are experiencing a heart attack. The new high sensitivity tests also help reduce emergency department overcrowding by enabling physicians to rule out a heart attack diagnosis in low-risk patients.[5],[6]</p>
Waiting for troponin I test results
Recommendations published jointly in 2018 by the American Association for Clinical Chemistry (AACC) and the International Federation of Clinical Chemistry (IFCC) create uniform, sex-specific cut off points so that an increased cTn concentration is defined as a value exceeding the 99th percentile of a normal reference population.[7] The recommendations also standardize the reporting of cTn levels in whole numbers, using ng/L without decimal points, and emphasize the importance of quality control and communication among clinicians.
Fred S. Apple, PhD, Medical Director of Clinical Laboratories at the Hennepin County Medical Center in Minneapolis, Minnesota, USA and a professor at the University of Minnesota Department of Laboratory Medicine and Pathology, noted that the use of high-sensitivity cardiac troponin testing benefits patients and the health care system as a whole.
“It's a precise assay, so with a very low value at presentation, you can get 30 to 50% of patients that are sent home for a huge cost savings to the health care system,” says Apple, who chaired IFCC Task Force on Clinical Applications of Cardiac Bio-Markers.[8] “On the other side, with early diagnosis in two hours, proper management, and proper drug therapy, we will see huge improvement in health care outcomes.”
<p>Siemens Healthineers offers lab-based high-sensitivity troponin I assays on four different analyzers and recently introduced high-sensitivity testing at the point of care with the Atellica® VTLi Patient-side Immunoassay Analyzer<sup>1</sup>. The handheld device, powered by Magnotech® Technology, provides clinicians with accurate, actionable results in as little as eight minutes utilizing a fingerstick or venous sample.</p>
Utilizing the finger stick selection, the clinician has the option to omit a more time-consuming blood draw for high-sensitivity troponin testing and improve ED throughput may be realized. In addition to offering speed and convenience, the <a href="https://www.siemens-healthineers.com/cardiac/cardiac-assays/vtli-hsctni" target="_blank">Atellica® VTLi system</a> offers a level of analytical performance and diagnostic accuracy that is equivalent to a lab-based assay.
“I believe this point-of-care system could easily integrate into existing hospital and clinic workflows, with the potential to impact patient care and clinical outcomes with operational and financial efficiencies,” Apple says.[9]
<p>The urgency of receiving appropriate treatment following a heart attack is summed up in the oft-repeated adage that time is muscle. For a patient, the ability to receive a rapid and reliable measurement of troponin levels can mean the difference between a timely treatment, whether that be through optimal medical therapy alone or <a href="percutaneous coronary intervention (PCI)">percutaneous coronary intervention (PCI)</a>, and a delayed treatment that results in a poor outcome. </p>
In this minimally invasive procedure a catheter is inserted through an artery to a blockage. A balloon is inflated to widen the blocked artery and in some cases a wire mesh stent is deployed to support the artery wall and prevent re-narrowing.
Cardiovascular diseases represent nearly a third of all global deaths,[10] and survivors of cardiovascular events experience losses in productivity for themselves and their caretakers that rival the direct costs of their treatment.[11]
Leading causes of death globally
For the majority of patients who present to the emergency department with chest pain that is not caused by a heart attack, the ability to receive a timelier rule out of an acute coronary syndrome means they can be discharged from the emergency department sooner and receive appropriate follow-up care in a non-urgent setting.
<p>The overcrowding of emergency departments that suspected myocardial infarctions contribute to is more than just an inconvenience. It is a major global healthcare issue that makes it more difficult for clinicians to adhere to evidence-based best practices that are associated with better outcomes for all patients.[12]</p>
Without new solutions, the problem is expected to worsen due to an aging population and the growing prevalence of risk factors such as obesity and diabetes. Globally, the incidence of ischemic heart disease, the narrowing of arteries that can lead to a heart attack, is expected to rise 11% over the next decade alone.[13]
Global incidence of cardiovascular disease
Apple emphasizes that high-sensitivity cardiac troponin testing at the point-of-care has the potential to benefit individual patients and the health care system as a whole by reducing dangerous and costly emergency department overcrowding.
<p>“To me the most powerful part of these high-sensitivity assays is early rule out; moving patients through your system, through your emergency department earlier to allow other patients to be seen in the emergency department,” Apple says[14].</p>

By Sameh Fahmy
Sameh Fahmy, MS, is an award-winning freelance medical and technology journalist based in Athens, Georgia, USA.