Evaluation of analytical performance of Advia® Tnl ultra immunoassay and comparison with Access® AccuTnl™ method

Objective. -We evaluated and compared the analytical and clinical performance of the Tnl-Ultra immunoassay for cardiac Troponin I (cTnl) measurement, carried out on the fully automated ADVIA Centaur and ADVIA Centaur CP (R) platforms (Siemens Medical Solutions Diagnostics SrL), and that of Access AccuTnl (TM), carried out on the UniCell (R) DxI 800 platform (Beckman Coulter, Inc., Fullerton). Methods. -We assayed 645 plasma Li-heparin samples of healthy subjects and 230 of patients with cardiovascular diseases (70 with a cTnl value higher than the decision Level for acute myocardial infarction) by Tnl-Ultra and Access AccuTnl (TM) immunoassays. Results. -The total imprecision (CV) profile of Tnl-Ultra method was determined by repeatedly measuring 19 plasma pools, with different concentrations of Tnl, in 20 different runs using two reagent lots; the CV ranged from 25% (at 0.02 mu g/L) to less than 5% (for levels greater than 0.4 mu g/L). On average, functional sensitivity (i.e. concentration measured with an imprecision of 10% CV) of Tnl-Ultra method was 0.057 The 99th percentile of normal distribution, calculated by enrolling a control group of 645 healthy subjects (278 mates and 367 females; mean age of 47.4 +/- 16.2 years, range 15-89 years), was 0.072 mu g/L. Therefore, the ratio between functional sensitivity and 99th percentile values was less than I (i.e., 0.057/0.072 = 0.79), white for Access AccuTnl (TM) resulted 0.07/0.06 = 1.16. A close linear regression was found between the cTnl values obtained with the two methods only when the samples of patients with cardiac disease were taken into account (Tnl-Uttra = -0.192 + 1.434 AccuTnl(T); R = 0.976; n = 230). A significant bias was found between the two methods by means of Bland-Altman plot (mean difference 38.9%), but when 368 healthy subjects were considered, no significant linear regression was found between these two methods (R = 0.002, p = 0.9624). Conclusion. - Our results indicate that the Tnl-Uttra immunoassay carried out on the fully automated ADVIA Centaur platforms shows analytical characteristics we[[ in agreement with the quality specifications recommended for cardiac troponin assay. (D 2008 Elsevier Masson SAS. ALL rights reserved.