Fig. 4

Comparison of plasma AβX–42/X–40 vs. Aβ1–42/1–40 by Bootstrapping statistics and receiver operating characteristic analysis. A–C histograms of the magnitude of the group differences in plasma AβX–42/X–40 (6E10) vs. Aβ1–42/1–40 (3D6) between amyloid-positive and amyloid-negative subjects observed after .632 bootstrapping are shown. A relative median difference, B relative mean difference and C Cohen’s d as measures of effect size. The indicated p-values were not corrected for multiple comparisons. The dashed lines show the respective means. D Receiver operating characteristic (ROC) analysis for plasma Aβ1–42/1–40 and AβX–42/X–40. Single value receiver operating characteristic (ROC) curves for the discrimination between amyloid-positive and amyloid-negative subjects were calculated for the plasma ratios Aβ1–42/1–40 and AβX–42/X–40 measured with mAb 3D6 and 6E10, respectively. The areas under the curves (AUCs) and the p-value are indicated. Aβ amyloid-β, mAb monoclonal antibody