Table 2.

Performance of plasma Aβ42/40 ratio for predicting amyloid PET status

		% (95% CI)
Sample set	Cutoff	Sensitivity	Specificity	PPV	NPV
Discovery	0.102	96.0 (90.1–98.9)	83.5 (74.6–90.3)	85.7 (77.8–91.6)	95.3 (88.4–98.7)
Validation		88.0 (80.0–93.6)	72.0 (62.1–80.5)	75.9 (67.0–83.3)	85.7 (76.4–92.4)

The cutoff value was determined by maximizing the Youden Index. The 95% CIs were calculated based on the Clopper-Pearson exact CI

Abbreviations: Aβ β-amyloid, PET Positron emission tomography, CI Confidence interval, PPV Positive-predictive value, NPV Negative-predictive value