Troponin-based protocol pinpoints low-risk chest pain patients
MedWire News: A 2-hour accelerated diagnostic protocol (ADP), with troponin I as the only biomarker, identifies a large proportion of patients with chest pain who are very unlikely to have a major adverse cardiac event (MACE) in the immediate future, say researchers.
The 30-day MACE rate was just 0.25% in this group of patients, report Martin Than (Christchurch Hospital, New Zealand) and colleagues.
"These patients could have been safely discharged to outpatient follow-up many hours earlier than what usually occurs in current practice," they write in the Journal of the American College of Cardiology.
"The reduction in time required for observation for some patients through application of this ADP could have significant benefits for health services, even in those centers with chest pain observation units."
Than et al note that, after lengthy diagnostic assessments, up to 85% of patients with suspected acute coronary syndromes (ASC) are given other diagnoses.
The ADP tested in their study included troponin I testing at arrival and 2 hours later, an electrocardiogram (ECG), and calculation of Thrombolysis In Myocardial Infarction (TIMI) score.
The team prospectively tested the ADP in 1975 patients with ACS symptoms. Of these patients, 20% were identified as low risk, having both troponin I values within accepted levels, no ischemic changes on ECG, and a TIMI score of 0. During the next 30 days, just one of these patients had a MACE, giving the ADP a sensitivity of 99.7% and a specificity of 23.4%, a negative predictive value of 99.7% and a positive predictive value of 19.0%.
Expanding the low-risk definition to include a TIMI score of 1 resulted in 38.4% of patients being classified as low risk. But nine of these patients had a MACE, giving a sensitivity of 97.0% and a specificity of 44.8%, a negative predictive value of 98.8% and a positive predictive value of 24.1%.
Than and team note that about three-quarters of patients classified as low risk by the ADP (with TIMI=0) underwent further diagnostic tests, most commonly stress tests.
They also point out that their study refutes the need for biomarker assessment beyond troponin I (such as myoglobin and creatine kinase-MB). Indeed, they argue that inclusion of these biomarkers would reduce the number of patients classified as low risk, and therefore the effectiveness of the ADP strategy.
The team concludes: "The components required for this strategy are already widely available; therefore, rapid uptake of the ADP is possible by most hospitals with the potential for immediate health service benefit."
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By Eleanor McDermid