More than just accuracy: A pathway-level framework for implementing blood and digital biomarkers for Alzheimer's disease care.

Blood biomarkers are transforming Alzheimer's disease diagnostics by enabling a scalable, minimally invasive assessment of pathology. Food and Drug Administration clearances and European market certifications of different plasma tests mark a shift toward biological diagnosis in routine care. However, clinical implementation is not guided by diagnostic accuracy alone but will depend on improved patient-centered and pathway-level outcomes, including diagnostic confidence, the appropriate use of CSF and PET assessments, time to diagnosis, amyloid-targeting treatment eligibility assessment, and trial recruitment. Digital biomarkers may complement blood tests by providing repeated measures of cognition, speech, and mobility. Yet, their evidence base remains more heterogeneous regarding construct validity, supervision requirements, device dependence, adherence burden, cultural portability, interpretability, and regulatory classification. This review defines how combined blood-digital workflows could be evaluated beyond accuracy, including the context of use, downstream decisions, ethical aspects, governance, and post-market monitoring, ultimately aiming to translate biomarker innovation into meaningful benefits for patients and health systems.