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Title: Evaluation of the analytical performance of the advanced method for cardiac troponin I for the AxSYM platform: comparison with the old method and the Access system.
Author: Storti S, Prontera C, Parri MS, Iervasi A, Vittorini S, Emdin M, Zucchelli GC, Longombardo G, Migliorini P, Clerico A.
Journal: Clin Chem Lab Med; 2006; 44(8):1022-9. PubMed ID: 16879072.
Abstract:
BACKGROUND: The determination of cardiac troponins is routinely used for rule in/out, risk stratification, and follow-up of patients with acute coronary artery syndrome. We evaluated the analytical and clinical performance of the advanced immunoassay for troponin I (cTnI) carried out on an AxSYM platform (Abbott Diagnostic Division) and compared these characteristics to those of the previous version of this assay and to cTnI on the Access 2 immunoassay system (Beckman Coulter, Inc.). METHODS: We assayed plasma samples from healthy subjects (n=66) and cardiac patients (n=132) using AxSYM Plus system assays called the old (OLD AxSYM) and advanced TnI (ADV AxSYM) methods and using an Access system. RESULTS: An improvement in analytical sensitivity (detection limit) was observed for the advanced cTnI AxSYM compared to the previous method (0.014 vs. 0.31 microg/L), while the cTnI value for the 10% CV (i.e., functional sensitivity) was 0.41 microg/L for the ADV and 1.9 microg/L for the OLD method. The kinetics of cTnI release was similar, as evaluated in 25 patients with typical acute myocardial infarction (AMI). A close linear relationship was found between the two methods on the AxSYM system (OLD cTnI=7.436+6.858 ADV cTnI; R=0.968, n=214) and with the Access system (OLD AxSYM=7.154+7.9 Access, R=0.876, n=158; ADV AxSYM=0.23+1.209 Access, R=0.927, n=160). However, wide bias was found between the OLD and ADV AxSYM methods (mean difference 118.4 microg/L, p<0.0001), while more similar results were found between the ADV AxSYM and Access methods (mean difference 2.6 microg/L, corresponding to a mean percentage difference of 17%, p<0.0001). In 106 patients with symptomatic rheumatoid arthritis with high rheumatoid factor (RF) concentration, the mean cTnI measured by the ADV AxSYM method was 0.009+/-0.031 mug/L (range 0-0.23 microg/L) with a significant correlation (R=0.316, p=0.001) between cTnI and RF values. Furthermore, in 60 of these serum samples the cTnI concentration was also measured using the Access method; significant correlation with the values found by the ADV AxSYM method was observed (R=0.468, p=0.0002). CONCLUSIONS: The present study indicates that the AxSYM Troponin-I ADV immunoassay shows improved analytical sensitivity compared to the OLD AxSYM method, as well as very similar clinical results to those determined using the Access method.

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