Abstract 16624: Impact of Troponin I Cut-Off Values on the Incidence of Myocardial Infarction With Non-ST-Segment Elevation: From a Higher Sensitivity to a True Greater Predictive Value?
Background: The diagnosis of myocardial infarction with non-ST-segment elevation (NSTEMI) is the result of a rule-out strategy, which strongly relies on cardiac biomarker elevations. However, the diagnostic management is sometimes complicated by confounding drawbacks, such as biomarker increases attributable to causes different from acute myocardial ischemia or cut-off value heterogeneity among laboratories, which may potentially affect the final epidemiological values of NSTEMI incidence.
Objective: To evaluate the impact of different Troponin I cut-off values on the annual incidence of NSTEMI.
Methods: From the codified hospital discharge registry (ICD-10 codes) of two hospitals of Canton Ticino (Mendrisio and Locarno) in Switzerland, we assessed the mean annual incidence of NSTEMI per 100’000 inhabitants before (2003-2004) and after (2008-2009) the change in Troponin I cut-off value from 0.1 to .01 ug/L (Biomérieux, VIDAS), this latter corresponding to the 99th percentile of the normal reference population, as proposed by the consensus guidelines.
Results: In the hospital of Locarno, the mean annual incidence of NSTEMI per 100.000 inhabitants was significantly higher during the period of high sensitivity Troponin assay (43.5 vs. 16.8, p-value 0.0036, Poisson regression) with a 2.6-fold increase in comparison to the period before the change in Troponin cut-off. Similarly, in Mendrisio hospital, the mean annual incidence of NSTEMI per 100.000 inhabitants was significantly higher during the period of high sensitivity Troponin assay (42.9 vs. 26.1, p-value 0.0209) with a 1.6-fold increase in comparison to the period before the change in Troponin cut-off. In both hospitals, population aging (from 2003 till 2009) had no significant effect on the increase of NSTEMI annual incidence (p-value >0.05).
Conclusions: In both hospitals of Canton Ticino, the Troponin I test with greater sensitivity (.01 ug/L) was associated with a significantly higher annual incidence of NSTEMI, not affected by population aging. Such retrospective results should suggest a certain caution in the introduction of high-sensitive assays and their evaluation in a proper diagnostic management able to rule-out false positive biomarker elevations for acute myocardial ischemia.
- © 2013 by American Heart Association, Inc.