2.6 Statistical analysis
The normal distribution of the data was analyzed by the D’Agostino &
Pearson Omnibus normality test. To select the cut-off with maximum
sensitivity and specificity, ROC curves were made by plotting these
parameters against the corresponding cut-off values. Statistical
significance was assessed by parametric tests: Student’s t-test for
unpaired samples with Welch correction; or non-parametric tests:
Mann-Whitney U test for unpaired data, when applicable. Calculations
were performed using GraphPad Prism version 6.01 for Windows (GraphPad
Software, San Diego California, USA, www.graphpad.com). A value of p
<0.05 was considered statistically significant.