READ-OUT observational study will investigate blood-based biomarkers for dementia in real-world clinical settings. This 3-year observational study will include 3165 people, males or females aged 45 years or older, with cognitive impairment of any severity.

Participants provide blood samples and complete questionnaires about quality of life and healthcare use, with some having additional follow-ups at 2 weeks and 1 year. The study will assess reliability and accuracy of blood tests in diagnosing dementia.

Dementia affects a growing number of people in the UK, with significant costs for individuals, families, and society. There is an urgent need for accurate diagnosis of dementia to allow early intervention and support when people can still make decisions about their care.

Current dementia diagnosis in memory clinics relies on clinical assessment, cognitive testing, and brain scans (MRI or CT). Only a small proportion of UK patients have access to more specific tests like PET brain scans or spinal fluid analysis, which are expensive and not widely available.

Recent developments have shown that blood tests can accurately detect the underlying brain changes of dementia, particularly Alzheimer's disease. In research studies, these blood-based biomarkers (ptau217, AB42/40 ratio, GFAP, NFL etc) have successfully identified people with Alzheimer's disease when compared to clinical diagnoses, gold standard brain scans, and post-mortem brain examination. These blood tests also show promise for predicting people with future dementia risk.

However, most research has been conducted in younger, less diverse populations than those seen in real-world memory services. Blood-based biomarkers are not yet used in routine NHS practice, and more work is needed to test how well they perform in representative UK populations. We also need to understand whether people want to know their blood test results, what information they want, and how this is best communicated.

The READ-OUT study will test blood-based biomarkers in people attending memory clinics across the UK (30 NHS sites), ensuring participants represent the full diversity of people with dementia or memory concerns (30% from underrepresented groups). Participants will provide a 40ml blood sample and complete questionnaires about quality of life, healthcare use, and attitudes toward blood testing for dementia. The accuracy of blood biomarkers will be compared against established diagnostic methods including expert clinical review, brain scans, spinal fluid tests, and long-term health record follow-up.

The study includes three optional sub-studies: test-retest reliability of blood biomarkers (10% of participants returning after 1-2 weeks), investigating disease progression over one year (20% of participants), and evaluating whether people can collect blood samples at home using finger-prick cards (75 participants).

The study will determine which blood biomarkers are most accurate for diagnosing different types of dementia, predict disease progression, and assess their cost-effectiveness in the healthcare system. Results will inform whether these tests should be integrated into NHS clinical pathways and will guide the design of READ-OUT Phase 2, a randomized trial testing whether providing blood biomarker results to patients and doctors improves clinical care and outcomes.

Inclusion Criteria:

The participant may enter the study if ALL of the following apply:

• Willing and able to give informed consent for participation in the study (translation needs for study information and forms for non-English speakers will be defined locally) OR Adults who otherwise lack the capacity to consent but for whom advice regarding participation has been obtained via a consultee using the personal or nominated consultee process
• Male or Female, aged 45 years and above
• Referred or referable with cognitive or behavioural symptoms and/or diagnosed with a cognition related disorder; including those with subjective cognitive impairment and functional disorders.

Exclusion Criteria:

The participant may not enter the study if ANY of the following apply:

• Lack of venous access
• Unwilling to consent to NHS data linkage or in Northern Ireland, unwilling to allow long term follow up by access to electronic NHS records.

People referred to, eligible for referral or already under review at primary and/or secondary memory assessment services (including memory clinics, brain health clinics) with some form of cognitive symptoms and/or cognitive disorders of any severity will be eligible for recruitment. Also, we recruit a subset of individuals who are not under a secondary care memory clinic but who have a clinical picture that would be suitable for secondary care assessment in memory clinic services.

Anonymised (linked) BBM and genetic data will be available for access (not copying/export) via the DPUK Data Portal (https://portal.dementiasplatform.uk/) upon an approved data/sample access proposal. It offers a secure, fully auditable data repository (currently facilitating access to data for over 3.6m individuals across more than 60 cohorts). A curated (standardised/harmonised) dataset will be made available to eligible researchers within the DPUK Trusted Research Environment (TRE) which is at the core of the Data Portal.