The measurement of cardiac troponin T (cTnT) is a powerful tool for the diagnosis of myocardial injury. Recently, a rapid bedside whole-blood quantitative cTnT assay has been developed. We evaluated the reliability of this test for the diagnosis of myocardial injury in patients with acute coronary syndrome (ACS).
Whole-blood cTnT levels were measured in 96 patients with ACS using the bedside Roche Cardiac Reader® and were compared with serum cTnT levels of the same patients measured by the Roche Elecsys® Immunoanalyzer. Forty patients (Group A) had clinical evidence of myocardial injury (13 with unstable angina and 27 with acute myocardial infarction) and 56 had no clinical evidence of myocardial injury (Group B). The cut-off value of cTnT used to assess for myocardial injury was 0.1 ng/ml.
Bedside cTnT tests were positive in 36 patients in Group A and 3 patients in Group B with a sensitivity, specificity and positive and negative predictive values of 90%, 95%, 92% and 93%, respectively. From qualitative point of view (reporting negative or positive tests), these results were identical to those obtained by the serum immunoanalyzer. From quantitative point of view,bedside tests could not measure the exact values below 0.1 ng/ml (reported negative) or above 2.0 ng/ml (reported > 2.0). Measurements by the bedside tests over the range of 0.1 and 2.0 ng/ml correlated well with those of the serum immunoanalyzer (r = 0.88), but their mean values were significantly lower (mean ± SD, 1.20 ± 0.71 vs. 1.41 ± 1.03, p = 0.0007).CONCLUSIONS: Bedside cTnT assays are very sensitive and specific for the diagnosis of myocardial injury and correlate well with the immunoanalyzer measurements between the values of 0.1 and 2.0 ng/ml. However, they tend to give significantly lower values and fail to give exact values below 0.1 and above 2.0 ng/ml, which may affect their performance in monitoring and managing patients with ACS and limit their use in predicting outcome.
S. Saadeddin, None.