POINT-OF-CARE TESTING
High-sensitivity troponin tests have the potential to improve patient flow and reduce waiting times at emergency departments.
infarction, which requires timely diagnosis and treatment. Conversely, the majority of patients who present with chest pain do not have a final diagnosis of coronary disease. About 50% of patients can be discharged without further hospitalisation with more than 80% of patients being discharged with a non-cardiac cause. The challenge has always been to quickly identify the group who do not have active coronary artery disease and can therefore be sent home or directed to the appropriate form of care, and to rapidly admit those where the suspicion of coronary disease is very high.
The advent of high-sensitivity
troponin measurements has resulted in the development of rapid assessment pathways. On the basis of a single test on admission, or serial testing on admission and one or two hours later, these rapid protocols can efficiently categorise approximately 80% of all those who present and potentially discharge around 50-60 % either immediately or within one to two hours. This represents a considerable improvement on the typical five to six hour (or often longer) wait in the
emergency department which seems to be the norm at present.
Could you provide insights into the background and the needs that drive the Mersey Acute Coronary Syndrome Rule Out Study (MACROS-2)? PC: Although we know that rapid algorithms based on high-sensitivity troponin measurements have the potential to achieve rapid diagnosis, this is based largely on observational studies. Whilst no published study has currently been able to demonstrate a significant improvement in patient throughput, there are a number of studies coming up to completion with promising preliminary evidence. These studies may further supplement the limited randomised controlled data currently available.
In addition, no laboratory can achieve
a turnaround time from blood being taken to the result being presented to the clinician of less than 45 minutes, which is the absolute requirement to implement these rapid pathways. The MACROS-2 study is pioneered and run by Professor Aleem Khand in Liverpool, who I have had the privilege
of being able to assist. All credit goes to him and his team and especially to the support they have had from the clinical biochemistry laboratory. The primary study is to compare the safety and efficacy of the 0-1 hour and 0-3 hour rapid measurement strategies proposed and endorsed by the European Society of Cardiology, using laboratory based high-sensitivity troponin. Additionally, because of the design of the study we have been able to perform measurements of high-sensitivity troponin using novel technology that measures a high-sensitivity troponin by point-of-care testing. These measurements are performed in real time and by non-laboratory staff. This is therefore a unique opportunity to evaluate how this technology will work in the real world. The MACROS-2 study is the first clinical validation of whole-blood point-of-care high-sensitivity troponin assays, studied at real time in a clinical environment.
It is vital that rapid assessment pathways are defined that will hinge around the rapid provision of an ECG and troponin result as soon as the patient arrives in the emergency department
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What key findings or standout points emerged from the MACROS-2 study? PC: The final data from the study have not yet been analysed but it is our feeling that both the 0-1 hour and 0-3 hour pathway are clinically safe. However, the 0-1 hour pathway does not appear to deliver significantly faster patient flow. This is because patient assessment is often limited by the turnaround time of blood results from the central laboratory. There are similar findings in other studies. We have been impressed by the diagnostic efficiency of the point-of-
OCTOBER 2024
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