Blood Tests for Alzheimer's Disease: Can Plasma Biomarkers Diagnose and Predict Disease Progression

Inclusion Criteria (main study and sub-study): 1. Age greater than or equal to 40 years (patients of childbearing age are admitted). 2. Subjective or objective cognitive complaints, progressive in nature and of suspected neurodegenerative origin. 3. Mini-Mental State Examination (MMSE) score greater than or equal to 18. Additional inclusion criterion for the validation sub-study: 4. Availability of CSF biomarkers for Alzheimer's disease within 6 months of the blood draw. Exclusion Criteria (main study): 1. Secondary forms of cognitive impairment based on medical history, neurological examination, and neuroimaging findings. 2. Pregnancy or breastfeeding. 3. Rapidly progressive cognitive decline occurring over weeks or months, typically indicative of prion disease, neoplasia, or metabolic disorders. 4. Subjects who require a legal guardian or tutor. Exclusion Criteria (validation sub-study): 1. Secondary forms of cognitive impairment based on medical history, neurological examination, and neuroimaging findings. 2. Pregnancy. 3. Rapidly progressive cognitive decline occurring over weeks or months, typically indicative of prion disease, neoplasia, or metabolic disorders. 4. Subjects who are unable to give informed consent and require a legal guardian or tutor.