ROC analysis applied to the DI. ROC curve is depicted as a solid black line, interspersed by blank dots representing the values of sensitivity and specificity (repeatability) associated to single DI values.

<p>The optimal DI value of 1.67% computed according to the Younden index <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0010281#pone.0010281-Younden1" target="_blank">[34]</a> is shown as a black dot. Dashed line represents the ROC curve of a random classifier. Gray-shaded region indicates the area under the curve.