Table 3.

Performance characteristics for detecting positive emission tomography (PET) status in the Alzheimer’s Disease Research Center (ADRC) cohort at 0.160 (maximum of Youden’s J index) and 0.170 (likely PET-negative) cutpoints, and the effect of prevalence and bias (bold=performance based on measured prevalence of PET positivity in full ADRC cohort).

Plasma Aβ42/40 Cutpoint	Prevalence (%)	Bias (%)	Sensitivity (95%, CI)	Specificity (95%, CI)	Accuracy (95%, CI)	PPV (95%, CI)	NPV (95%, CI)
0.160	40	none	0.911 (0.842–0.970)	0.758 (0.678–0.832)	0.820 (0.772–0.864)	0.719 (0.656–0.788)	0.926 (0.876–0.974)
0.160	34*	none	0.857 (0.738–0.976)	0.659 (0.537–0.768)	0.726 (0.645–0.798)	0.563 (0.478–0.661)	0.900 (0.820–0.980)
0.160	34*	22†	0.333 (0.167–0.500)	0.854 (0.756–0.939)	0.677 (0.605–0.742)	0.538 (0.346–0.737)	0.714 (0.663–0.771)
0.160	34*	2‡	0.762 (0.619–0.905)	0.671 (0.549–0.780)	0.702 (0.621–0.782)	0.542 (0.446–0.649)	0.846 (0.762–0.932)
0.170	40	none	0.990 (0.960–1.000)	0.537 (0.443–0.624)	0.720 (0.672–0.768)	0.592 (0.546–0.643)	0.988 (0.953–1.000)
0.170	34*	none	0.976 (0.905–1.000)	0.476 (0.354–0.598)	0.645 (0.573–0.718)	0.488 (0.433–0.554)	0.975 (0.907–1.000)
0.170	34*	22†	0.429 (0.262–0.595)	0.829 (0.732–0.915)	0.694 (0.621–0.766)	0.563 (0.400–0.732)	0.739 (0.681–0.802)
0.170	34*	2‡	0.929 (0.833–1.000)	0.537 (0.415–0.659)	0.669 (0.589–0.742)	0.506 (0.441–0.583)	0.936 (0.851–1.000)

^*Amyloid positivity by PET in the ADRC cohort—MCI group only

^†+10% bias in Aβ42 and -10% bias in Aβ40 = 22% total bias per Rabe, et al.¹³

^‡+2% total measured bias in the LC-MS/MS assay