BACKGROUND: A cardiac troponin concentration above the 99th percentile limit of a reference population is a sensitive marker of myocardial necrosis. Current guidelines require troponin assays to have a total imprecision of <or =10% at the 99th percentile limit. In this study, the Advia Centaur second-generation TnI-Ultra assay was validated and compared with its predecessor the cardiac troponin I (cTnI) assay, with a focus on the current guidelines for diagnosis of acute myocardial damage. METHODS: An imprecision profile of the TnI-Ultra assay was evaluated by analysing different pools over 20 days. The imprecision of the cTnI assay was used as comparison. The reference range was established based on TnI-Ultra analysis in 221 individuals. RESULTS: The cTnI concentration that could be determined with a total imprecision of 10% was 0.05 microg/L for the TnI-Ultra assay and 0.3 microg/L for the cTnI assay. The 99th percentile limit in the distribution of a reference population was 0.06 microg/L as determined with the TnI-Ultra assay. CONCLUSIONS: The TnI-Ultra assay provides significantly improved sensitivity when compared with the cTnI assay and a total imprecision of <or =10% is obtained at the 99th percentile limit of value distribution of a reference population. Using the TnI-Ultra assay, slightly increased cTnI concentration can be detected reliably following the current guidelines.