Enhancing Alzheimer's disease diagnosis in primary care through targeted screening of people at risk of developing dementia - study design and feasibility assessment of the PREDEM primary care study.

BACKGROUND: Timely detection of cognitive impairment due to Alzheimer's disease (AD) is increasingly important as disease modifying therapies become available. Current diagnostic pathways in primary health care (PHC) rely mainly on clinical assessment and brief cognitive screening tools, which lack sensitivity for early impairment. Blood-based biomarkers (BBMs) show promising diagnostic potential in research settings. Targeted screening of individuals with cognitive symptoms and dementia risk factors using sensitive cognitive tests and reliable biomarkers may improve early AD detection in PHC. The PREDEM primary care study evaluates a targeted screening strategy combining a multidomain digital cognitive test battery and BBMs in individuals having elevated risk of dementia. This pilot study assessed the feasibility of recruitment, digital cognitive testing, biomarker sampling, and data collection. METHODS: This descriptive pilot study was conducted at two PHC centres in Stockholm (April-October 2024). Eligible individuals were aged ≥ 65 years with hypertension or type 2 diabetes and self-reported memory complaints. Participants completed a screening question, followed by a demographic questionnaire, a multidomain digital cognitive test battery (Mindmore), MMSE, and blood sampling for four BBMs (GFAP, NF‑L, total tau, pTau217). Feasibility metrics included recruitment yield, test completion rates, participant characteristics, cognitive performance, and biomarker distributions. RESULTS: Of 548 identified individuals, 307 were invited and 40 were enrolled (13% participation). Among those enrolled, 37 completed all parts of the study. Digital home-based testing proved challenging: although 22 participants initially opted for home testing, only six completed it independently, and most required clinic-based support. Across cognitive tests, approximately one-third of participants scored below 1 standard deviation of normative performance, indicating detectable cognitive impairment. Non-native Swedish speakers (32%) showed significantly lower performance on verbally mediated tasks. Established cut-off values for pTau217 reflecting amyloid pathology showed pathological levels in 10-23% of participants depending on single or double cut-offs. CONCLUSIONS: This pilot study demonstrates the feasibility of the PREDEM primary care study design and data collection procedures. Targeted recruitment of older adults with cardiometabolic risk factors was able to identify a population relevant to the study aims. Key protocol refinements include removing the requirement for subjective memory complaints, conducting all cognitive testing at PHC, and optimization of cognitive test battery.