Abstract 14950: Absolute Change in Highly Sensitive Troponin T Concentration 2 Hours After an Initial Sample Out-Performs Other Highly Sensitive Troponin Diagnostic Models for the Early Diagnosis of Myocardial Infarction
The current universal definition of MI requires the observation of a rise or fall in troponin for the diagnosis of acute MI. Conventionally, a relative change (delta) of 20% is taken as significant. However, the utility of this delta value is unknown with highly sensitive assays of troponin. We hypothesised that the recently proposed absolute change in highly sensitive troponin T (hsTnT) of 7ng/l in 2 hours will provide improved diagnostic discrimination and classification than other delta values and admission hsTnT ≥14ng/l alone.
Following admission venesection, serial samples were obtained at 1, 2, 3, 6, 12 and 24 hours. Published 99th centile upper reference limits provided the diagnostic thresholds for MI. No imputation for missing data was performed.
In total, 548 consecutive patients from two UK centres with possible ischaemic chest pain were recruited between October 2009 and September 2011. Symptom onset to first venesection was less than 6 hours (mean 3.6hrs, SD 1.3hrs) in 359 patients included in this analysis. Of these 359 patients, 113 (31.5%) had a final adjudicated diagnosis of MI; 59 (16.4%) with ST-segment elevation and 54 (15.0%) without ST-segment elevation.
Admission sample C-Statistics for diagnosis of MI were; hsTnT 0.90 (95%CI 0.87-0.95), hsTnT and relative change at 3 hours 0.96 (0.93-0.98, P=0.003), hsTnT and absolute change 0-2hrs 0.96 (0.95-0.98, P=<0.001). Net Reclassification Index (NRI) was significantly greater with hsTnT models incorporating absolute change of ≥7ng/l than admission hsTnT ≥14ng/l in isolation. Models including relative change in hsTnT did not improve reclassification relative to admission hsTnT (Table 1).
In conclusion, we have confirmed the improved diagnostic accuracy of absolute change in hsTnT of ≥7ng/l from 0-2hrs when compared to an admission hsTnT ≥14ng/l in isolation. This improvement is greater than that seen with other delta value models.
- © 2012 by American Heart Association, Inc.