Alzheimer’s early detection: innovative blood test shows reliability of around 90 percent
Detecting Alzheimer’s-related changes before symptoms become visible
Alzheimer’s dementia is one of the most common neurodegenerative diseases worldwide, but nowadays it is often only diagnosed when noticeable damage to the brain has already occurred. This late diagnosis considerably limits the treatment options. With the approval of the antibody lecanemab in Europe as well, it was hoped that politicians and society would have had to urgently address the unresolved issues and make important decisions with regard to the necessary improvement of the infrastructure for early diagnosis.
However, the drug was rejected by the EMA due to the massive side effects and the associated risks for patients, who should at best have been affected at a very early stage of dementia, so that the associated, possibly faster refinancing of cerebrospinal fluid examinations, for example, is likely to be a long time coming.
The current professional tenor is that the focus should continue to be on prevention in order to curb the number of cases of Alzheimer’s and dementia. Other promising, optional therapy methods, for example on a physical basis (non-invasive brain stimulation – NIBS) for Alzheimer’s patients are not yet established and widespread enough to compensate for this. However, there is good news from the field of early detection in the form of a blood test that is as simple as it is innovative.
New Alzheimer’s blood test proves extremely effective in primary healthcare
Until now, the early changes in the brain that precede Alzheimer’s disease can only be detected using positron emission tomography (PET). Another option is to measure amyloid and tau proteins in the cerebrospinal fluid (CSF). However, both methods are invasive, cost-intensive and require considerable effort. Research has therefore focused intensively on the development of blood tests that could enable early and reliable diagnosis. A promising approach that is attracting a great deal of international attention now comes from Sweden: Researchers at Lund University have developed a blood test that can detect changes in the brain two decades before the onset of dementia symptoms.
New blood test: Phospho-Tau217 as a key indicator
The test is based on the detection of the phosphorylated tau protein at threonine 217 (P-tau217) in blood plasma. This protein plays a central role in the formation of neurofibrillary tangles, which are characteristic of Alzheimer’s pathology. Various tau variants have been investigated as biomarkers in the past, but the Swedish approach focuses specifically on P-tau217, which showed exceptionally high diagnostic accuracy in the current study.
Convincing results in several cohorts
The study comprised three independent cohorts with a total of 1,402 participants, including patients with Alzheimer’s dementia as well as those with other neurodegenerative diseases and healthy controls. In the first cohort, which was conducted in Arizona, the test was able to achieve a diagnostic accuracy (area under the curve, AUC) of 0.89 in participants with neuropathologically confirmed Alzheimer’s dementia. This means that the blood test not only outperformed other biomarkers measured in plasma such as P-tau181 and neurofilament light chain (NfL), but also came very close to the accuracy of more invasive methods such as the measurement of P-tau in cerebrospinal fluid.
In the Swedish BioFINDER-2 cohort, which included a larger and more diverse group, the test even achieved an AUC of 0.96 in distinguishing Alzheimer’s dementia from other neurodegenerative diseases. This shows that P-tau217 in plasma has a particularly high sensitivity and specificity and is therefore an extremely reliable indicator for Alzheimer’s disease.
Detection of preclinical Alzheimer’s stages as early as 20 years before the onset of cognitive symptoms
The ability of the new test to detect pathological changes very early in the course of the disease is particularly impressive. In the third cohort, which examined a group of carriers of the autosomal dominant PSEN1 E280A mutation in Colombia, the researchers were able to detect increased P-tau217 levels in plasma around 20 years before the estimated onset of the first cognitive symptoms. This suggests that the test is useful not only for diagnosis in the advanced stages of the disease, but also for detecting preclinical stages when therapeutic interventions may be most effective.
Comparison with established diagnostic methods
Imaging techniques such as positron emission tomography (PET) and cerebrospinal fluid biomarker analysis, currently the gold standard in Alzheimer’s diagnosis, are, as mentioned above, costly, invasive and logistically challenging. The new blood test offers a promising alternative. In direct comparisons, the test showed comparable diagnostic accuracy to the established methods, especially in differentiating Alzheimer’s from other neurodegenerative diseases. This could initiate a paradigm shift in clinical practice, as blood tests are much more widely available and easier to perform.
Great potential for clinical practice: patients could be treated earlier and more effectively
The blood test for P-tau217 could be particularly important in primary care and memory outpatient clinics, especially in regions with limited access to specialized diagnostic procedures. This applies not only to industrialized countries, but also to emerging countries where access to sophisticated imaging techniques is limited. Easy access to such a blood test could improve the early detection of Alzheimer’s globally and help to treat patients earlier and more effectively.
Challenges and next steps
Despite the promising results, there are still challenges that need to be overcome before the test can be put into clinical practice. The researchers are currently working on optimizing the accuracy of the test and developing a standardized assay that can be used in clinical laboratories worldwide. In addition, further studies are needed to validate the results in ethnically diverse and unselected populations.
An important step towards a new era of Alzheimer’s diagnostics
The blood test developed by Lund University could be a decisive step towards early and broad diagnosis of Alzheimer’s disease. With its high diagnostic accuracy and the ability to detect pathological changes long before the onset of clinical symptoms, this test has the potential to fundamentally change the treatment of Alzheimer’s disease. Accordingly, the blood test is already being used commercially in the USA. The coming years will show whether this promising approach can keep its promise and also be established in clinical practice in other countries. This could not only considerably improve the quality of life of those affected, but also significantly increase the effectiveness of new therapeutic approaches.
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