Evaluation of innotrac aio! Second-generation cardiac troponin I assay: the main characteristics for routine clinical use

The availability of a simple, sensitive, and rapid test using whole blood to facilitate processing and to reduce the turnaround time could improve the management of patients presenting with chest pain. The aim of this study was an evaluation of the Innotrac Aio! second-generation cardiac troponin I (cTnI) assay. The Innotrac Aio! second-generation cTnI assay was compared with the Abbott AxSYM first-generation cTnI, Beckman Access AccuTnI, and Innotrac Aio! first-generation cTnI assays. We studied serum samples from 15 patients with positive rheumatoid factor but with no indication of myocardial infarction (MI). Additionally, the stability of the sample with different matrices and the influence of hemodialysis on the cTnI concentration were evaluated. Within-assay CVs were 3.2%-10.9%, and between-assay precision ranged from 4.0% to 17.2% for cTnI. The functional sensitivity (CV = 20 %) and the concentration giving CV of 10% were approximated to be 0.02 and 0.04, respectively. The assay was found to be linear within the tested range of 0.063-111.6 mu g/L. The correlations between the second-generation Innotrac Aio!, Access, and AxSYM cTnI assays were good (r coefficients 0.947-0.966), but involved differences in the measured concentrations, and the biases were highest with cTnI at low concentrations. The second-generation Innotrac Aio! cTnI assay was found to be superior to the first-generation assay with regard to precision in the low concentration range. The stability of the cTnI level was best in the serum, lithium-heparin plasma, and lithium-heparin whole blood samples (n = 10 , decrease < 10 % in 24 hours at +20( degrees )C and at +4( degrees )C. There was no remarkable influence of hemodialysis on the cTnI release. False-positive cTnI values occurred in the presence of very high rheumatoid factor values, that is, over 3000 U/L. The 99th percentile of the apparently healthy reference group was </= 0.03 mu g/L. The results demonstrate the very good analytical performance of the second-generation Innotrac Aio! cTnI assay.

Altered complexity and correlation properties of R-R interval dynamics before the spontaneous onset of paroxysmal atrial fibrillation

BACKGROUND

Trigger mechanisms for the onset of paroxysmal atrial fibrillation (AF) in patients without structural heart disease are not well established. New analysis methods of heart rate (HR) variability based on nonlinear system theory may reveal features and abnormalities in R-R interval behavior that are not detectable by traditional analysis methods. The purpose of this study was to reveal possible alterations in the dynamics of R-R intervals before the spontaneous onset of paroxysmal AF.

METHODS AND RESULTS

Traditional time and frequency domain HR variability indices, along with the short-term scaling exponent alpha(1) and approximate entropy (ApEn), were analyzed in 20-minute intervals before 92 episodes of spontaneous, paroxysmal AF in 22 patients without structural heart disease. Traditional HR variability measures showed no significant changes before the onset of AF. A progressive decrease occurred both in ApEn (1.09+/-0.26 120 to 100 minutes before AF; 0.88+/-0.24 20 to 0 minutes before AF; P<0.001) and in alpha(1) (1.01+/-0.28 120 to 100 minutes before AF, 0.89+/-0.28 20 to 0 minutes before AF; P<0.05) before the AF episodes. Both ApEn (0. 89+/-0.27 versus 1.02+/-0.30; P<0.05) and alpha(1) (0.91+/-0.28 versus 1.27+/-0.21; P<0.001) were also lower before the onset of AF compared with values obtained from matched healthy control subjects.

CONCLUSIONS

A decrease in the complexity of R-R intervals and altered fractal properties in short-term R-R interval dynamics precede the spontaneous onset of AF in patients with no structural heart disease. Further studies are needed to determine the physiological correlates of these new, nonlinear HR variability measures.