The clinical and diagnostic performance characteristics of the high sensitivity Abbott cardiac troponin I assay

Objectives: The aim of this study is to determine the imprecision profile, 99th percentile and diagnostic efficiency of a new high sensitivity cardiac troponin I (cTnI) assay.

Methods: Total imprecision was assessed by following CLSI protocol EP15-A.14. Serum pools prepared from sera of known high cardiac troponin concentrations were adjusted by dilution with serum considered to be troponin free. Determination of the 99th-percentile reference value examined a fully characterized population that had undergone non-invasive cardiac imaging. Diagnostic accuracy utilised samples from the point of care arm of the RATPAC trial (Randomised Assessment of Treatment using Panel Assay of Cardiac markers), set in the emergency departments of six hospitals. Blood samples were taken on admission and 90min from admission. Diagnosis was based on the universal definition of myocardial infarction utilising laboratory measurements of cardiac troponin performed at the participating sites together with measurements performed in a core laboratory and compared by construction of receiver operator characteristic curves.

Results: Total imprecision was 4%-12.1% with 10% CV of 7ng/L. cTnI was measureable in 99.5% of the samples. Troponin values were influenced by gender but not by age. The 99th percentile was 14.8ng/L (18.1 males, 8.6 females). Progressive filtering of the population reduced the 99th percentile. For the diagnosis of MI on admission the area under the curve was 0.92, statistically indistinguishable from four other assays studied (0.90-0.94).

Conclusion: The analytical performance of the new assay meets the criteria for a high sensitivity troponin assay.