Table 2.

Concordance of Elecsys CSF immunoassay biomarkers and biomarker ratios with amyloid PET

CSF biomarker	AUC (95% CI)	Cut-off		Sensitivity	Specificity
Aβ42	0.78 (0.68−0.88)	Pre-defined	< 1000 pg/mL	0.93	0.57
		Youden index	< 1070 pg/mL	1.00	0.57
pTau181	0.82 (0.73−0.90)	Pre-defined	> 27 pg/mL	0.69	0.80
		Youden index	> 22 pg/mL	0.83	0.71
tTau	0.78 (0.68−0.87)	Pre-defined	> 300 pg/mL	0.63	0.73
		Youden index	> 241 pg/mL	0.87	0.63
pTau181/Aβ42 ratio	0.88 (0.81−0.95)	Pre-defined	> 0.024	0.96	0.69
		Youden index	> 0.027	0.96	0.76
tTau/Aβ42 ratio	0.87 (0.80−0.95)	Pre-defined	> 0.28	0.92	0.69
		Youden index	> 0.33	0.91	0.78
Aβ42/40 ratio	0.90 (0.83−0.97)	Pre-defined	NA	NA	NA
		Youden index	< 0.048	0.94	0.82
pTau181/(Aβ42/40) ratio	0.87 (0.80−0.94)	Pre-defined	NA	NA	NA
		Youden index	> 447	0.92	0.76
tTau/(Aβ42/40) ratio	0.86 (0.79−0.94)	Pre-defined	NA	NA	NA
		Youden index	> 5164	0.94	0.73

Aβ amyloid beta, AUC area under the curve, CI confidence interval, CSF cerebrospinal fluid, NA not applicable, PET positron emission tomography, pTau181 phosphorylated tau 181, tTau total tau