Cardiac Troponins T and I: Reproducible Discrepancies in the Clinical Setting
What is the frequency of significant discrepant cardiac troponin T (cTnT) and cardiac troponin I (cTnI) results measured in the same patient?
The authors compared two different assays, the Architect cTnI assay (Abbott Diagnostics) and the new high-sensitive TnT (hsTnT) assay (Roche Diagnostics) in 9,004 simultaneous cTnI and cTnT measurements on 3,995 patients. Discrepant values were then compared. To exclude minor inconsistencies, only values in which one of the cTn assays was below the 0.032 ug/L cutoff value and the result for the other assay was at least 3 times that value, were included.
The majority of the discrepant results were explained by minor differences near the cutoff or by differences in cTn kinetics. Exclusion of these resulted in a total of 18 cases with discrepant TnT and TnI results. Nine were cTnI (+), hsTnT (-), and 9 were cTnI (-), hsTnT (+). Significant coronary disease was present in six of the nine cTnI (+) patients and three of nine hsTnT (+) patients. Renal failure was present in one of nine TnI (+) patients, and five of nine hsTnT (+) patients. Neither of the two was statistically different.
True discrepant results are rare, but do occur. It therefore might be helpful to confirm clinically equivocal increases or unexpectedly typical results obtained for one cTn by measuring the other.
This potentially important article points out that on occasion, there are substantial elevations of cTnT but not cTnI and vice versa, which are not easy to explain. Clinicians need to at least understand this possibility. The safest approach, assuming there are no analytic issues, would be to protect the patient and manage him/her as if the elevation is a real one.
Keywords: Renal Insufficiency, Biological Markers, Troponin I, Troponin T, Coronary Disease, Kinetics
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