When evaluating a continuous-scale diagnostic test, we need to account for the changes of specificity and sensitivity when the test threshold t varies. One may wish to report the sum of sensitivity and specificity at the optimal threshold (discussed later in greater detail). However, because the optimal value of t may not be relevant to a particular application, it can be helpful to plot sensitivity and specificity over a range of values of interest, as is done with an ROC curve. This inherent tradeoff between sensitivity and specificity also can be demonstrated by varying the choice of threshold.