[Macromolecular complex of cardiac troponin I: differences of reactivity with DPC and Dade-Behring assays]

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.