Fig. 1
ROC curves of plasma Aβ1–42/Aβ1–40 and Aβ1–42/t-tau to detect cerebral amyloidosis: ELISA versus SIMOA. ROC curves of plasma Aβ1–42/Aβ1–40 (left) and Aβ1–42/t-tau (right) are shown with amyloid-PET status as the standard-of-truth in the entire study population (n = 199) (a, b) as well as in the CN (n = 161) (c, d) and aMCI subgroup (n = 38) (e, f), when Aβ isoforms were measured with either ELISA (blue) or SIMOA assays (orange). Note that the AUCs for ELISA and SIMOA are based on plasma biomarker measurements on their own, without inclusion of age or APOE-ε4 genotype in the model. Additionally, the ROC curve of the basic demographic model, including only age and APOE-ε4 genotype, is shown (black) on each plot together with its corresponding AUC for the respective subgroups. Amyloid-PET positivity as binary input for ROC was defined as a SUVRcomp above a predefined cut-off of 1.38 for [18F]flutemetamol PET [21] and 1.29 for [18F]florbetaben PET. For calculation of these cut-offs, we used the same methodology as the one employed in a previous study [22]. aMCI, amnestic mild cognitive impairment; AUC, area under curve; Aβ, β-amyloid; CI, confidence interval; CN, cognitively normal; ROC, receiver operating characteristic; SIMOA, single molecule array; t-tau, total tau