Evaluation of two modified cardiac troponin I enzyme immunoassays

One of the major challenges for manufacturers of troponin immunoassays is to optimize the low-end of the assays because diagnostic and therapeutic interventions are based on decreasing cutpoints. Recently published consensus documents of the European Society of Cardiology and the American College of Cardiology recommended the 99th percentile of a reference control group as cut-off for increased troponin I levels and suggested that imprecision at the 99th percentile for each assay should be < or = 10%. In this study, we have evaluated two newly modified cardiac troponin I (cTnI) enzyme immunoassays (Dimension cTnI assay, Dade Behring, Germany and AIA-PACK cTnI 2nd-Gen, Eurogenetics Tosoh, Belgium). With both assays all measured cTnI values in plasma and serum samples of apparently healthy volunteers were within the reference ranges given by the manufacturers. Intra-assay coefficients of variation of cTnI concentrations above the 99th percentile (given by the manufacturers) were below 17% and decreased with increasing cTnI concentrations. In most samples, the AIA-PACK cTnI assay yielded higher results; however, a close correlation between both assays was observed. Both tests exhibit acceptable overall performance, but (especially the Dimension cTnI assay) do not yet meet the above-mentioned precision in the low-end assay range. These data emphasize the need for cTnI assay standardization and for further optimization at clinical decision levels.