Fig. 1: Study flow diagram for sample collection and processing.

Collection and processing of capillary blood samples. A finger-prick sample was completed by participants at home without supervision, supported by instructional materials. Completed kits were returned by post. Blood spots were collected and incubated with analyte-specific extraction buffer, centrifuged and analysed using immunoassays on the Simoa platform to analyse p-tau217 and GFAP concentration. Image created in Canva under the available content license agreement (https://www.canva.com/policies/content-license-agreement/) and in BioRender.com (https://www.biorender.com/) under the available license agreement. Images also replicated with permission from Huber et al.¹⁷.