How do point of care high-sensitivity tests compare to lab-based assays for acute coronary syndrome diagnosis?

Precise and sensitive diagnostic testing is key to enabling appropriate patient care, especially in an emergency department setting. In an exclusive interview, SelectScience^® speaks with Dr. Michael Samoszuk, Medical Officer at Siemens Healthineers, to find out how point of care (POC) high-sensitivity troponin assays enable quick and accurate decision making, which is crucial to timely diagnosis and treatment of acute coronary syndrome. He also sheds light on how POC assays perform compared to central lab tests, as he predicts how the future of troponin testing in hospitals is likely to evolve.

Troponin tests are frequently used worldwide in emergency medicine to help diagnose a heart attack, known as an acute myocardial infarction, in patients who present with chest pain or other relevant symptoms. Heart attacks can be triggered by blood clots in coronary arteries, in a condition known as acute coronary syndrome (ACS). “Troponin tests are widely acknowledged to be one of the most important steps in making an ACS diagnosis, based on which clinicians can make follow-up treatment decisions. If a person suffers from a moderate to a severe heart attack, a lab-based troponin assay can detect it in a manner sufficient to inform clinical decision making,” says Samoszuk.

The need for sensitivity in emergency medicine

Clinicians make an ACS diagnosis by evaluating the significance of troponin levels or the change in these levels over time. The readout differentiating a normal measurement from an abnormal one is used to determine whether a patient is admitted, observed for a longer period of time or discharged. Hence, clinicians need access to assays that are sensitive and reliable, especially when evaluating borderline values of troponin elevation to make decisions. However, conventional troponin assays have limited sensitivity, coupled with turnaround times of over an hour. Due to this, patients with borderline troponin level variations may need to be observed for long periods of time to be accurately diagnosed with lab-based troponin assays. This waiting period can be detrimental in emergency department settings for the patients, as well as the care providers: it has been associated with poor patient outcomes, overcrowding, as well as an increased administrative burden.

High-sensitivity cardiac troponin tests (hs-cTn) – high precision assays that can detect very low levels of troponin elevation – offer an advantage over conventional cardiac troponin assays. Patients may require only one troponin test to confirm a diagnosis, as opposed to having repeat tests over several hours. However, these tests are typically performed by the central laboratory and there is still a demand for an accurate, faster, and easier way to obtain these results. Now new POC hs-cTn assays are available to clinicians, offering a solution that could change the way ACS patients are managed.

The benefits and considerations in performing high-sensitivity tests at POC

POC hs-cTn assays allow clinicians to leverage the analytical performance of the high-sensitivity assay, with the added advantages of speed, accessibility, and ease of use. Where a typical laboratory test requires wait times of over an hour, the POC assay provides results in a matter of minutes. The latter is also efficient, providing savings in terms of time, costs, sample and space: “The hs-cTn assay can be performed on a small and simple device that takes up very little room, and is easy to operate by a relatively untrained user. The test itself is also non-invasive, requiring a small sample of blood - using a fingerstick - which is easy to obtain. It’s a revolutionary development to be able to get a fast, accurate result from a small device at the patient’s bedside,” explains Samoszuk.

Moreover, normal troponin ranges also exhibit gender-specific variations, which is another avenue where the hs-cTn test can prove useful, says Samoszuk: “Men and women present with different kinds of symptoms for cardiac ischemia and heart attacks. They also have different 99th percentile cut-offs to define normal troponin levels, which is lower for women than for men.” When presented with atypical symptoms that may or may not be a heart attack in an emergency department, the sensitivity of the troponin test becomes critical to interpreting the results in the context of gender-specific troponin reference ranges and cut-off points. Thus, the hs-cTn can help detect and accurately diagnose ACS in the different genders, even at lower levels of troponin elevation.

With all its advantages, it is important to note that POC troponin testing also yields results that are comparable - both analytically and clinically - to that from a core laboratory. This does come with an important caveat that the numbers generated by the two instruments will not be identical, cautions Samoszuk. “Regardless of the manufacturer, or the source of the assay, it is a well-established fact that numerical troponin results will vary from instrument to instrument. While the exact numbers cannot be compared, if the test is positive from the main lab, the test will be positive with the POC device as well. The analytical interpretation, the precision, the linearity, and the accuracy will all be comparable or equivalent for both devices,” he adds.

The place of POC testing in the future

Samoszuk predicts that POC and lab-based tests will remain integrated alongside each other in future clinical settings. With the significant advantages in terms of time savings and confidence levels that the POC device provides, it is likely to be used more in emergency department settings for initial assessment and evaluation of patients. The automated analyzers in the laboratory, on the other hand, may be more apt for already hospitalized patients who exhibit symptoms of cardiac ischemia or acute myocardial infarction. “Each test type has a unique place and value for assessing the clinical status of different populations. They are complementary and will continue to co-exist, even potentially being used as a backup for one another to inform accurate ACS diagnosis and care,” concludes Samoszuk.

Learn more about the impact of high-sensitivity cardiac troponin testing at the point of care by watching our video series with leading clinicians on The Scientists’ Channel.