Use absolute cTn change for AMI diagnosis, advise researchers
MedWire News: Absolute changes in cardiac troponin (cTn) levels provide significantly greater diagnostic accuracy for acute myocardial infarction (AMI) than relative changes, a study indicates.
Current guidelines for the diagnosis of AMI require a "significant rise and/or fall" in cTn levels, but do not specify whether to assess relative or absolute changes in cTn or the amount of change required to be considered significant, explain Tobias Reichlin (University Hospital Basel, Switzerland) and colleagues in the journal Circulation.
To investigate this issue, Reichlin and colleagues studied 836 patients presenting to the emergency department with AMI symptoms, such as acute chest pain. The team collected blood samples for high-sensitivity cTn T and cTn I ultra, the current "gold standard" for AMI detection, upon presentation and at 1 and 2 hours afterwards. Diagnosis of AMI was then adjudicated by two independent cardiologists.
Receiver-operating characteristic area under the curve (AUC) analysis showed that the diagnostic accuracy of absolute cTn changes after 2 hours for AMI diagnosis was higher than that of 2-hour relative changes (cTn T: 0.95 vs 0.76, cTn I ultra: 0.95 vs 0.72, p<0.001 for both).
Further analysis showed that the AUC-derived cutoff value for 2-hour absolute change was 0.007 µg/l for high-sensitivity cTn T and 0.020 µg/l for cTn I ultra.
"Regardless of baseline levels, absolute changes were superior compared with relative changes for both assays at all time points," report the authors.
"These results indicate that absolute rather than relative cTn changes should be used in the assessment of patients with suspected AMI," they conclude.
In a related commentary, editorialist Fred Apple (University of Minnesota, Minneapolis, USA) wrote: "We need a better understanding of how high-sensitivity cardiac troponin assays improve patient care through earlier and more accurate diagnosis.
"Reichlin and co-workers describe important information that may be applied toward addressing this goal."
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By Piriya Mahendra