Fig. 1

Schematics of the study workflow. Baseline blood plasma samples from 203 individuals with subjective cognitive decline (SCD) were analyzed. Plasma samples were circulated over the iRS surface. Antibodies bound on the surface catch all isoforms of Aβ out from the plasma. The readout is the infrared frequency of the amide I band of all antibody-bound Aβs. This frequency is indicative of the Aβ secondary structure distribution in plasma. Frequencies above 1646 cm^− 1 in green represent a normal secondary structure distribution, as found in healthy subjects. Frequencies below 1646 cm^− 1 indicate low misfolding (yellow), and those below 1644 cm^− 1 (red) indicate high misfolding as observed in AD-affected individuals. The predictive performance of the structure biomarker was validated with clinical diagnosis at 6 years of follow-up. SCD = subjective cognitive decline; MCI = mild cognitive impairment; AD = Alzheimer’s disease; OD = other dementia