[NT-proBNP measurement on Immulite 2500 (DPC): analytical performance and comparison with Roche Diagnostics and Dade-Behring NT-proBNP immunoassays]. / Dosage du NT-proBNP sur l'Immulite 2500 (DPC): évaluation analytique et comparaison avec les trousses Roche-Diagnostics et Dade-Behring.

The measurement of the N-terminal part of the proBNP (NT-proBNP) may be used to assess the secretion of the B-type natriuretic peptide (BNP), a marker of heart failure. In this study, we have evaluated the NT-proBNP immunoassay proposed by DPC Company for the Immulite 2500 analyzer and compared the results with those obtained with the two other immunoassays respectively commercialized by Roche Diagnostics (Elecsys 2010 analyzer) and Dade-Behring (Dimension RXL). The obtained results show very good general performance of the DPC's technique with a CV inferior to 8% for the values superior to 40 ng/L. The within run CVs are 3.1, 3.5 and 3.5% and the between run CVs are 3.8, 4.7 and 4.8% for the NT-proBNP levels of 151, 1601 and 5255 ng/L, respectively. We found a very good correlation between DPC's and Roche Diagnostics's assays (regression analysis: y = 0.88 x + 25.2 ; r = 0.998) and DPC's and Dade-Behring assays (regression analysis: y = 0.93 x + 16.4 ; r = 0.997). Although a small bias appeared between these assays, similar cut-points may be used to exclude both heart failure in ambulatory patients and cardiac origin in acute dyspnea.

[Macromolecular complex of cardiac troponin I: differences of reactivity with DPC and Dade-Behring assays]. / Complexe macromoléculaire de troponine I cardiaque: différence de réactivité des trousses de dosage DPC et Dade-Behring.

We have recently identified a macromolecular 440-kDa cardiac troponin I (cTnI) complex after successful percutaneous transluminal coronary angioplasty (PTCA) (Clin Chem 2003; 49: 505-7). The aim of the work was to confirm the existence of such a complex by using another cTnI assay (Dimension RXL, Dade-Behring). We have first studied the correlation between the two assays by using heparinized samples [cTnI(Immulite) = 2.00 cTnI(Dimension) - 0.01 (n = 176; r = 0,987)]. Then, cTnI taken 120 minutes after PTCA for two patients was measured with the two assays after fractionation by FPLC. The obtained results confirmed the existence of the 440-kDa cTnI complex and showed that the reactivity between the assays (DPC/Dade-Behring ratio) depended on the nature of the complex: the ratio increased from 0.7 (440-kDa cTnI complex) to 3 (80-kDa cTnI complex) therefore suggesting caution in the comparison between the different cTnI assays in the context of reperfusion therapy.