The calculation of the cardiac troponin T 99th percentile of the reference population is affected by age, gender, and population selection : a multicenter study in Italy

Background: The aim of this study is to determine the 99th upper-reference limit (URL) for cardiac troponin T (cTnT) in Italian apparently healthy subjects. Methods: The reference population was selected from 5 cities: Bolzano (n = 290), Milano (CAMELIA-Study, n = 287), Montignoso (MEHLP-Study, n = 306), Pisa (n = 182), and Reggio Calabria (MAREA-Study, n = 535). Subjects having cardiac/systemic acute/chronic diseases were excluded. Participants to MEHLP project underwent cardiac imaging investigation. High-sensitive cTnT was measured with Cobas-e411 (Roche Diagnostics). Results: We enrolled 1600 healthy subjects [54.6% males; age range 10-90. years; mean (SD): 36.4 (21.2) years], including 34.6% aged <20. years, 54.5% between 20 and 64 years, and 10.9% over 65 years. In the youngest the 99th URL was 10.9 ng/L in males and 6.8 ng/L in females; in adults 23.2 ng/L and 10.2 ng/L; and in elderly 36.8 ng/L and 28.6 ng/L. After the exclusion of outliers the 99th URL values were significantly decreased (P < 0.05) in particular those of the oldest (13.8 ng/L and 14 ng/L). MEHLP participants were divided in healthy and asymptomatic, according to known cardiovascular risk factors (HDL, LDL, glucose, C-reactive protein): the 99th URL of cTnT values of these subgroups was significantly different (19.5 vs. 22.7, P < 0.05). Conclusions: 99th URL of cTnT values was strongly affected by age, gender, selection of subjects and the statistical evaluation of outliers.