Distribution of plasma cardiac troponin I values in healthy subjects: pathophysiological considerations

Background: The aim of this study was to evaluate the distribution of cardiac troponin I (cTnI) values, measured by the ADVIA TnI-Ultra method (Siemens Medical Solutions Diagnostics SrL) in healthy subjects and to characterize its relation to gender, age, as well as to N-terminal fragment of pro-brain natriuretic peptide (NT-proBNP). Methods: A Caucasian population of 692 healthy subjects (311 males and 381 females) with a mean (SD) age of 45.3 (17.3) years [range 11-89 years; females 46.5 (17.3) years, males 43.8 (17.1) years] was enrolled. The presence of cardiac or systemic acute or chronic diseases was excluded by history and accurate clinical evaluation. Results: A significant difference was found between the cTnI values in men and women (men: median 0.012 mu g/L, range from undetectable values to 0.196 mu g/L; women: median 0.008 mu g/L, range from undetectable values to 0.130 mu g/L; p < 0.0001 by Mann-Whitney U-test). When a multiple regression analysis was performed, NT-proBNP, gender and age significantly contributed to the regression with cTnI (R=0.444, p < 0.0001). Conclusions: Our data indicate that cut-off values, based on the 99th percentile of cTnI distribution in apparently healthy subjects, can significantly vary according to age and gender of the reference population.