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  • Author: K. Kleesiek x
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We have evaluated the cardiac troponin I (cTnI) enzyme immunoassay AIA-PACK cTnI 2G (Tosoh Bioscience). The interassay precision at different cTnI levels (0.30 6.70 ng/ml-1) showed coefficients of variation (CV) between 5.00% and 4.71% on the AIA 600 II instrument. These data are in accordance with the functional sensitivity (0.04 ng/ml-1) and analytical sensitivity (0.02 ng/ml-1) specified by the manufacturers. Comparative troponin I measurements in serum samples were performed on the AIA-600 II analyser (Tosoh Bioscience) and the Dimension RxL analyser (Dade Behring). The cTnI concentration of serum samples (n=226) ranged from 0 ng/ml-1 to 114 ng/ml-1. Regression analysis of the cTnI values obtained showed a close correlation between both results (RxL=0.96 AIA+0.38; r=0.960). To induce proteolytic in vitro degradation of the cTnI molecule, patient serum samples (n=20) were incubated at 37C for 24 h and the cTnI concentration was determined before and after the incubation with both analysers. The cTnI concentration measured with the AIA-600 II analyser showed nearly identical values before and after the incubation period. However, cTnI measured with the Dimension RxL analyser showed decreased cTnI values in a range of 10 to 50% after the incubation period. The AIA-PACK cTnI 2G assay uses two different monoclonal antibodies against two epitopes in the proteolytic stable region of the cTnI molecule (between position 40 and 90 of the cTnI amino acid sequence). Therefore, measurement of cTnI in serum remains precise and specific in spite of in vitro proteolysis.