FIG 3.

(a) Empirical provirus receiver operating characteristic (ROC) curves for naturally infected study cats, including uninfected cats (n = 201) and provirus-positive (p27 positive and p27 negative) cats (n = 35). The true-positive rate (sensitivity, y axis) is plotted against the false-positive rate (1 − specificity, x axis) at various cutoff points. (b) Determination of the optimal cutoff for naturally infected cats. The sensitivity × specificity (y axis) is plotted against the cutoff (x axis). Dark lines represent specificities of ≥80%. The arrows indicate the cutoff points for each antigen.