A rapid troponin I assay is not optimal for determination of troponin status and prediction of subsequent cardiac events at suspicion of unstable coronary syndromes

Background: Troponin is a specific marker of myocardial damage. For early prediction of coronary events in patients with suspicion of acute coronary syndromes the assay also needs to be highly sensitive. Methods and results: A rapid troponin I assay was performed prior to inclusion in 4447 acute coronary syndrome patients in the GUSTO-IV trial. A quantitative troponin T analysis was later performed on blood samples obtained at randomization by a central laboratory. There was an agreement between the rapid troponin I assay and troponin T (≤/>0.1 μg/l) in 3596 (80.9%) patients. A positive rapid troponin I was identifying any elevation of troponin T (>0.01 μg/l) in 1990 patients (90.4%) whereas a negative rapid troponin I was corresponding to negative troponin T (≤0.01 μg/l) in only 1217 patients (54.2%). Patients with a positive versus negative rapid troponin I had an increased risk of death or myocardial infarction at 30 days (9.3 vs. 5.9%; odds ratio, O.R. 1.64; 95% confidence interval, 1.31–2.06). Troponin T elevation (>0.1 μg/l) provided a better (10.5 v. 4.9%, O.R. 2.26; C.I. 1.79–2.85) risk stratification. Regardless of a positive or a negative rapid troponin I, the troponin T result (>0.1 vs. ≤0.1 μg/l) stratified the patients into high and low risk of events at 30 days, (10.3 vs. 5.7%, P=0.002) and (11.5 vs. 4.8%, P<0.001), respectively. Conclusion: In a population with non-ST elevation acute coronary syndrome a positive rapid troponin I assay is a specific indicator of troponin elevation and a predictor of early outcome. However, a negative rapid troponin I is not a reliable indicator of the absence of myocardial damage and does not indicate a low risk of subsequent cardiac events. A rapid troponin I assay was performed prior to inclusion in 4447 acute coronary syndrome patients in the GUSTO-IV trial and related to a centrally analyzed quantitative troponin T test. A positive rapid troponin I was well corresponding to any elevation of troponin T (>0.01 μg/l) and predicted an unfavorable outcome at 30 days. However, a negative rapid troponin I was corresponding to troponin T ≤0.01 μg/l in only half of the patients. Troponin T >0.1 μg/l vs. ≤0.1 μg/l provided a better risk stratification than the rapid troponin I result. For patients with troponin T elevation (>0.1 μg/l) the 30 day event rate was high regardless of the rapid troponin I result.