Role of monitoring changes in sensitive cardiac troponin I assay results for early diagnosis of myocardial infarction and prediction of risk of adverse events.

BACKGROUND

We sought to determine the diagnostic accuracy of the cardiac troponin I (cTnI) VITROS(R) Troponin I-ES assay for early detection of acute myocardial infarction (AMI) and for risk prediction of adverse events in patients with symptoms of acute coronary syndrome (ACS).

METHODS

cTnI was measured on admission and approximately 6 h postadmission in 381 patients. The 99th percentile cTnI concentration (0.034 microg/L) and change [delta (delta)] between admission and follow-up concentrations were evaluated in diagnostic sensitivity and specificity calculations. Risk of cardiac event or death within 60 days was evaluated by Cox proportional hazards regression.

RESULTS

AMI occurred in 52 patients. Diagnostic sensitivities (95% CI) of admission and follow-up cTnIs for AMI were 69% (55%-81%) and 94% (84%-99%), respectively. The corresponding specificities (95% CI) were 78% (73%-82%) and 81% (77%-85%), and ROC curve areas were 0.82 vs 0.96 (P < 0.001). Deltas between admission and follow-up cTnI >30% had a sensitivity of 75% (95% CI 61%-86%) and a specificity of 91% (95% CI 87%-94%). During follow-up, 1 cardiac death, 2 noncardiac deaths, 52 AMIs, 6 coronary artery bypass grafts, and 43 percutanous coronary interventions occurred in 62 patients. A delta cTnI >30%, when added to either initial cTnI >0.034 microg/L or follow-up cTnI >0.034 microg/L, improved risk stratification for cardiac event or death (P < 0.001).

CONCLUSIONS

Admission cTnI measured by the VITROS ES assay is a sensitive biomarker for detection of AMI. Utilizing >30% cTnI delta in addition to either the baseline or follow-up concentration improved both specificity and risk assessment in patients presenting with symptoms of ACS.