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Table 2 Performance of plasma Aβ42/40 ratio for predicting amyloid PET status

From: Fully automated and highly specific plasma β-amyloid immunoassays predict β-amyloid status defined by amyloid positron emission tomography with high accuracy

   % (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)
  1. The cutoff value was determined by maximizing the Youden Index. The 95% CIs were calculated based on the Clopper-Pearson exact CI
  2. Abbreviations: β-amyloid, PET Positron emission tomography, CI Confidence interval, PPV Positive-predictive value, NPV Negative-predictive value