Clinical performance of cardiac Troponin I: A comparison between the POCT AQT90 FLEX and the Dimension Vista analyzer in an emergency setting.

ABSTRACT

BACKGROUND: Cardiac troponin [cTn (I or T)] is the preferred biomarker for the diagnosis of myocardial infarction (MI). AIM: We studied the analytical performance of the POCT AQT90 FLEX cTnI assay and its diagnostic accuracy, in comparison to the Dimension Vista cTnI method, in patients presenting to the Emergency Department (ED) with suspect of acute coronary syndrome (ACS). METHODS: 786 consecutive patients were enrolled. cTnI was measured at admission to the ED and about 3 and 6 hours later. The imprecision study was carried out using different lots of quality controls (QCs). ROC curve analysis was conducted using discharge diagnoses in order to verify the global diagnostic accuracy. RESULTS: The concentrations measured in the QCs ranging from 0.033 to 1.26µg/L show CVs% ranging from 2.81 to 7.56%, comparable to those declared by the manufacturer. Passing-Bablok and linear regression analysis show a high significant correlation (R2=0.90, p<0.0001); Bland-Altman test describes a statistically significant negative bias (Bias=-0.2336; 95%CI=-0.4217/-0.0456, p=0.0150). ROC curves obtained using Dimension Vista and AQT90 FLEX cTnI assays displayed similar clinical performance being not statistically significant the difference of the corresponding AUC. Comparing sensitivity and specificity of cTnI concentrations obtained from the ROC curve analysis using AQT90 FLEX, we found a "best cut-off" (0.014µg/L) lower than that declared from the manufacturer (0.023µg/L). CONCLUSIONS: The comparison of two different assays of cTnI against a diagnosis of acute MI (AMI) shows that both assays behave equally well with a high degree of sensitivity and specificity. The resulting "best cut-off" suggests that this AQT90 FLEX cTnI concentration could be evaluated as the potentially new "clinically usable" cut-off for AMI/myocardial necrosis diagnoses.