For decades, confirming Alzheimer's required a lumbar puncture or a £3,000 PET scan. That has fundamentally changed.
June 2026 · 8 min read · Lambert Medical Clinical Team
Alzheimer's disease affects over 900,000 people in the UK, yet for most of this century, definitive diagnosis required either an invasive lumbar puncture or an expensive PET brain scan — both largely inaccessible outside major academic medical centres. In the last two years, that has changed dramatically. A simple blood test can now detect the hallmark pathology of Alzheimer's disease with over 90% accuracy.
This article explains the science behind the new blood tests, what they measure, how accurate they really are, and — crucially — why early detection has never mattered more than it does right now.
It is important to start with a distinction. Alzheimer's disease is diagnosed clinically — based on cognitive symptoms, history, and the exclusion of other causes. What the new blood tests detect is amyloid pathology: the presence of amyloid plaques in the brain.
Amyloid plaques are the most established hallmark of Alzheimer's disease. They begin accumulating years — sometimes decades — before symptoms appear. Detecting amyloid pathology in a symptomatic patient is now considered strong evidence that Alzheimer's is the underlying cause of their cognitive decline. It is this that the blood tests measure.
Phosphorylated tau at amino acid 217 (pTau217) is a protein found in elevated concentrations in the blood of people who have amyloid plaques in their brain. When amyloid accumulates, it triggers abnormal phosphorylation of the tau protein — and this signal appears in the bloodstream. The Alzheimer's Association Workgroup has identified plasma pTau217 as the most accurate single blood-based biomarker for detecting amyloid pathology, with accuracy comparable to cerebrospinal fluid tests.
The LucentAD® Complete test — available at Lambert Medical Practice — measures five biomarkers simultaneously from a standard blood plasma sample:
The primary biomarker. Directly reflects amyloid plaque burden. Highly specific to Alzheimer's pathology.
Glial fibrillary acidic protein. Reflects astrocytic activation in the brain, which occurs in concert with amyloid pathogenesis.
Neurofilament light chain. A general biomarker of neuronal damage occurring in neurodegenerative diseases.
Directly reflects amyloid plaque development. The ratio changes as more amyloid is deposited in the brain.
These five biomarkers are combined using a validated multi-variate algorithm to generate a single Amyloid Risk Score from 0 to 100. A score below 45 indicates low likelihood of amyloid pathology. Above 70 indicates high likelihood. Between 45 and 70 is an intermediate result requiring further investigation.
LucentAD® Complete was validated in 1,082 patients across three independent international cohorts — the Amsterdam Dementia Cohort, the BioHermes multi-site trial (with emphasis on ethnic diversity), and the ADNI longitudinal cohort. The results were robust:
Overall accuracy
Sensitivity
Specificity
Intermediate results
Critically, 90% of patients receive a definitive high-risk or low-risk result — only approximately 10% fall in the intermediate zone. This compares very favourably to earlier single-biomarker tests, where intermediate results affected up to 30% of patients. The test meets the performance standards set by both the Alzheimer's Association Workgroup and the Global CEO Initiative on Alzheimer's Disease.
Early detection of Alzheimer's has always offered value — ruling out other treatable causes, enabling planning, supporting families. But in 2026, there is a more urgent clinical reason to test early: disease-modifying treatments are now available.
The MHRA has approved two anti-amyloid drugs:
Both drugs require confirmed amyloid-positive status before treatment can begin. Both are most effective when started at the earliest symptomatic stage — before significant neurological damage has occurred. Neither is currently available through the NHS, but both can be accessed privately.
Anti-amyloid drugs are approved for early symptomatic Alzheimer's — meaning mild cognitive impairment or mild dementia with confirmed amyloid pathology. By the time symptoms become moderate or severe, the therapeutic window has largely closed. This is why a blood test at the first sign of memory change or cognitive concern is clinically meaningful, not premature.
A high-risk result (score above 70) indicates a high likelihood of amyloid pathology, consistent with Alzheimer's disease. It does not, by itself, establish a diagnosis — that requires clinical assessment. Your GP will discuss the result with you, explain next steps, and refer you to a neurologist for full evaluation. If you are eligible, a referral for anti-amyloid treatment can be initiated.
It is also worth noting that amyloid pathology can be detected years before symptoms become clinically apparent. Some patients with high-risk scores are in the pre-symptomatic phase — where lifestyle interventions (exercise, sleep optimisation, cardiovascular risk management, cognitive engagement) have the greatest potential to slow progression.
A low-risk result (score below 45) is equally valuable. It rules out Alzheimer's amyloid pathology as the current cause of cognitive symptoms — directing attention to other, potentially very treatable, causes: thyroid dysfunction, vitamin B12 or D deficiency, anaemia, sleep apnoea, vascular disease, anxiety, depression, or medication side effects. All of these are far more common than Alzheimer's disease and entirely reversible when identified.
We offer the LucentAD® Complete test at our Surbiton clinic in partnership with Advance Tests, the UK's exclusive distributor. A standard venous blood sample is taken at the clinic — no lumbar puncture, no fasting, no preparation. Results are available in 15 working days. Every result is reviewed and discussed with you by one of our GPs, with clear guidance on next steps.
We also offer APOE genotyping as an optional add-on, which identifies the ε4 genetic variant — the strongest known genetic risk factor for late-onset Alzheimer's — and helps assess side-effect risk from lecanemab and donanemab.
LucentAD® Complete: 90% accuracy, 5 biomarkers, results in 15 working days. GP-interpreted.
pTau217 standalone · Complete panel £695
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