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High-sensitivity troponin T test improves sensitivity of ACS detection
10 March 2010
MedWire News: Researchers report that a high-sensitivity troponin T (hsTnT) test has increased sensitivity for acute coronary syndrome (ACS) compared with a conventional cardiac troponin T (cTnT) assay.
Udo Hoffman (Massachusetts General Hospital, Boston, USA) and colleagues compared the two tests in 337 patients, aged an average of 53.7 years, presenting in the emergency department with chest pain and low-to-intermediate likelihood of ACS.
The reference diagnosis of ACS was based on clinical and laboratory data including conventional serial troponin measurements and stress tests over 6 months of follow-up.
Patients also underwent 64-slice coronary computed tomography (CT) imaging at a median of 4.2 hours from initial presentation, at which time blood samples were taken for biomarker testing using a precommercial hsTnT assay and a conventional commercial cTnT method.
Using the cutpoint of the 99th percentile for a normal reference population, equating to 13 pg/ml, the hsTnT assay had 62% sensitivity for ACS, which was statistically superior to that of the cTnT test at its 99th percentile cutpoint of 0.01 ng/ml, at 49% (p=0.002).
The researchers report that hsTnT using the 13 pg/ml cutpoint also had excellent specificity, at 89%, although this was significantly less specific than cTnT at the 0.01 ng/ml cutpoint, at 97% (p<0.001).
The positive and negative predictive value of the hsTnT using the 13 p/ml cutpoint were 38% and 76%, respectively.
Overall, the hsTnT method detected 27% more ACS cases than did the cTnT method (p=0.001), Hoffman and colleagues report, and multivariable linear regression analysis confirmed that an hsTnT result above the 99th percentile strongly predicted ACS, at an odds ratio of 9.0.
The receiver operator characteristic optimal cutpoint for hsTnT was 8.62 pg/ml, which delivered 76% sensitivity, 78% specificity, and a 27% positive predictive value for ACS.
CT angiography demonstrated that hsTnT levels were determined by numerous factors independently of ACS diagnosis, including the presence and severity of coronary artery disease, left ventricular mass, left ventricular ejection fraction, and regional left ventricular dysfunction. Of note, 38 (62%) patients with a hsTnT result above 13 pg/ml who did not have ACS had more complex medical histories and more cardiac abnormalities than those without ACS and lower hsTnT levels.
This finding “illustrates the importance of considering hsTnT values not only as a marker of ACS presence but also as a marker of underlying structural heart disease,” the authors remark.
In a related editorial, George Diamond and Sanjay Kaul, from University of California in Los Angeles, USA, highlighted the impact of pretest probability on the diagnostic interpretation of any biomarker test, irrespective of diagnostic accuracy.
“Although hsTnT assays offer potential advantages over the conventional assays, the major problem with them, as with any other laboratory test, is often an inappropriate request and improper interpretation of the results, not the marker itself,” they wrote.
“Troponin evaluation should be performed only if clinically indicated, and elevated troponin should always be interpreted in the context of the clinical presentation.”
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