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J Am Coll Cardiol. 2010 May 11;55(19):2118-24. doi: 10.1016/j.jacc.2010.01.044.

Prospective evaluation of the prognostic implications of improved assay performance with a sensitive assay for cardiac troponin I.

Author information

1
TIMI Study Group, Cardiovascular Division, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA. mbonaca@partners.org

Abstract

OBJECTIVES:

The purpose of this study was to investigate the prognostic implications of low-level increases in cardiac troponin I (cTnI) using a current-generation sensitive assay in patients with suspected acute coronary syndrome (ACS).

BACKGROUND:

Recent enhancements in troponin assays have enabled resolution of the 99th percentile reference limit at progressively lower concentrations. However, the clinical significance of low-level increases with sensitive assays is still debated.

METHODS:

We measured cTnI using a sensitive assay (TnI-Ultra, Siemens Healthcare Diagnostics, Deerfield, Illinois) at baseline in 4,513 patients with non-ST-segment elevation ACS randomly assigned to ranolazine or placebo. We applied decision limits at the 99th percentile reference limit (0.04 microg/l), the cut point of the predecessor assay (0.1 microg/l), and 1 equivalent to elevation of creatine kinase-myocardial band (1.5 ng/ml).

RESULTS:

Patients with baseline cTnI > or =0.04 microg/l (n = 2,924) were at higher risk of death/myocardial infarction (MI) at 30 days than were patients with a negative cTnI (6.1% vs. 2.0%, p < 0.001). After adjusting for the TIMI (Thrombolysis In Myocardial Infarction) risk score, cTnI > or =0.04 microg/l was associated with a 3-fold (95% confidence interval: 2.0 to 4.4, p < 0.001) higher risk of death/MI at 30 days. Moreover, patients with low-level increases (0.04 microg/l to <0.1 microg/l), were at significantly higher risk of death/MI at 30 days (5.0% vs. 2.0%, p = 0.001) and death at 12 months (6.4% vs. 2.4%, p = 0.005) than were patients with cTnI <0.04 microg/l.

CONCLUSIONS:

Low-level increases in cTnI using a sensitive assay identify patients at higher risk of death or MI. These findings support current American College of Cardiology/American Heart Association recommendations defining MI, and the incremental value of newer, more sensitive assays in identifying high-risk patients with ACS.

PMID:
20447535
DOI:
10.1016/j.jacc.2010.01.044
[Indexed for MEDLINE]
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