Author + information
- Luis C.L. Correia, MD, PhD⁎ ( and )
- Márcia Noya-Rabelo, MD, MSc
- ↵⁎Medical School of Bahia, Avenue Princesa Leopoldina, 19/402, 40.150-080, Salvador, Bahia, Brazil
We read with interest the paper by Body et al. (1). In a cohort of 703 individuals with acute chest pain, Body et al. demonstrated that the use of a high-sensitivity troponin assay coupled with a low cutoff point (any detectable level) yields 100% sensitivity for recognizing myocardial infarction, leading to a perfect negative predictive value. Thus, the investigators concluded, “this strategy could be used to reduce unnecessary hospital admissions.” We intend to further analyze the implications of this approach.
First, in order to reduce the number of patients unnecessarily admitted to the hospital, a test should have an improved ability to recognize healthy individuals that can be safely discharged. The ability to recognize healthy people is defined as “specificity.” As one lowers the cutoff point of a test, sensitivity improves at the cost of specificity. In fact, along with the increase in sensitivity from 85% to 100%, the investigators reported a decrease in specificity from 82% to 34% as the lower cutoff was adopted. Because a smaller number of healthy people will be identified, it is highly questionable if this approach really reduces unnecessary admissions. Even if different cutoff points were adopted to rule out and rule in infarction, a gray zone of confusion would be created, leading to considerable doubt if this strategy would be useful in clinical practice.
Second, if the lower cutoff point is used only to rule out infarction, how many patients will be discharged by this new approach? Body et al. showed that 28% of the cohort had negative troponin, ensuring no infarction. However, the study did not report how many of those were really discharged. From those patients, some could have very typical chest pain, characterizing unstable angina; some could have ischemic electrocardiogram changes; and others could have other serious causes of chest pain that prevented discharge. Therefore, a negative troponin does not necessarily mean discharge and the actual number of patients in which the troponin result helped the decision is not clear in the paper.
The universal definition of infarction takes the 99th percentile of troponin as the cutoff point (2), providing good diagnostic accuracy (85% sensitivity and 82% specificity) (1). Before trading this accuracy for a higher sensitivity at the expense of specificity (so-called D-dimer approach), clinical evidence should demonstrate a real advantage over the traditional way of troponin interpretation. The definitive level of evidence will be ideally provided by randomized clinical trials comparing the 2 strategies.
- American College of Cardiology Foundation
- Body R.,
- Carley S.,
- McDowell G.,
- et al.
- Thygesen K.,
- Alpert J.S.,
- White H.D.,
- et al.,
- Joint ESC/ACCF/AHA/WHF Task Force