A new, more sensitive biomarker test for acute coronary syndrome (ACS) is associated with reduced time spent by a patient in emergency waiting for a diagnosis, but can result in investigations being performed unnecessarily on individuals without ACS, according to research published in the Medical Journal of Australia.
The cardiac troponin l (cTn-l) assay with increased sensitivity has recently been introduced into clinical practice in Australia, improving detection of lower levels of troponin, the biomarker of choice in aiding the diagnosis of acute myocardial infarction (AMI).
As a result, detectable cardiac troponin levels can be found even in healthy individuals, and the new test can be used to detect elevated levels in AMI at an earlier stage than possible with the older, less sensitive assays.
Researchers led by Dr Thomas Yip, from the Department of Cardiology at Barwon Health, analysed all patients presenting to the emergency department (ED) of Geelong Hospital with suspected acute coronary syndrome (ACS) from 23 April 2010 to 22 April 2013. The cTn-l assay was introduced at Geelong Hospital on 23 April 2012.
They measured admission rates, time spent in the ED, coronary angiography rates, invasive treatment rates, ACS diagnosis rates and rates of inhospital mortality due to ACS.
Dr Yip and his coauthors found that although there was no significant difference in either the hospital admission rates or the proportion of patients diagnosed with ACS, the median time patients spent in the ED was 11.5% shorter after the introduction of the higher sensitivity assay (3.85 versus 4.35 hours). The proportion of patients who underwent coronary angiography increased significantly, from 45.2% to 53.4%.
"Although there was an increase in the proportion of patients for whom coronary angiography was performed, there was no significant increase in invasive treatment or change in inhospital mortality", the authors concluded.
In an editorial in the same issue of the MJA, Professor Derek Chew, from the Department of Cardiovascular Medicine at Flinders Medical Centre in Adelaide, warned that "While increased sensitivity ensures that the problem of missed myocardial infarction (MI) is far less likely, it also creates the problem of reduced specificity. The consequence is a lower positive predictive value for MI when faced with a positive result".
"While troponin assays with higher analytic precision might offer improved patient outcomes through lower rates of missed MI, they could also increase the investigative burden borne by patients with abnormal test results because of the many non-coronary causes of detectable troponin."