The cerebrospinal fluid biomarker ratio Aβ42/40 identifies amyloid positron emission tomography positivity better than Aβ42 alone in a heterogeneous memory clinic cohort

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
Aβ42	0.78 (0.68−0.88)	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
pTau181	0.82 (0.73−0.90)	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
tTau	0.78 (0.68−0.87)	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
pTau181/Aβ42 ratio	0.88 (0.81−0.95)	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
tTau/Aβ42 ratio	0.87 (0.80−0.95)	Youden index	> 0.33	0.91	0.78
Aβ42/40 ratio	0.90 (0.83−0.97)	Pre-defined	NA	NA	NA
Aβ42/40 ratio	0.90 (0.83−0.97)	Youden index	< 0.048	0.94	0.82
pTau181/(Aβ42/40) ratio	0.87 (0.80−0.94)	Pre-defined	NA	NA	NA
pTau181/(Aβ42/40) ratio	0.87 (0.80−0.94)	Youden index	> 447	0.92	0.76
tTau/(Aβ42/40) ratio	0.86 (0.79−0.94)	Pre-defined	NA	NA	NA
tTau/(Aβ42/40) ratio	0.86 (0.79−0.94)	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

ISSN: 1758-9193