High-sensitivity cardiac troponin I in the clinical setting: a rapidly developing field

Substantial progress in the identificaion of patients at increased risk of cardiovascular disease has been made through the development of high-sensitivity troponin assays. These assays are used in increasingly diverse clinical settings, including preventive medicine. ¹ By way of example, high-sensitivity cardiac troponin I (hs-cTnI) has recently been reported to perform well at the 99th percentile of the reference population. ² hs-cTnI may be used to predict the development of unrecognized myocardial infarction (U-MI) in community-living older people, although the cutoff level for hs-cTnI for predicting U-MI was within the reference range, ³ and it is not clear if the identification of U-MI predicts future adverse outcomes in this population and setting. ² In other words, detection of high-normal levels of high-sensitivity troponin may be difficult to intepret in clinical settings such as primary prevention or screening in particular.

These recent papers^2,3 have contributed to the ongoing debate about overuse and overdiagnosis using cardiac troponin testing. ⁴ Some of the questions that arise are: How, to what extent or in what situations should hs-cTnI assays be used? What are the economic implications of hs-cTnI assays? The need for age-, gender- and race-specific reference intervals for hs-cTnI has been highlighted ¹ , and investigators agree on the need to standardize the currently available hs-TnI assays, since a 2.5-fold difference in the 99th percentile of the hs-cTnI level has been reported in these assays in healthy people. ⁵

Herein, we would further like to stress the added value of using repeated measurements in the same subject. For example, in the acute phase, the changes seen in 2-hour repeated measurements of hs-cTnI in comparison to at-baseline one-time measurement, may permit more accurate diagnosis of acute myocardial infarction. ¹ The optimal interval between the first and second measurements remains to be determined in not only acute, but also chronic settings (e.g. primary prevention or mass screening); a monitoring duration of within five years in a chronic phase may be proposed based on a recent paper about the association between hs-TnI and U-MI. ² More research ideas for improving the application of hs-cTnI in the clinical setting are needed.