A major obstacle in treating Alzheimer’s disease is that it is thought to begin long before patients show symptoms like memory loss. That not only makes treatment difficult but also hampers research into effective treatments.
But now scientists say they have developed a blood test that can detect early indicators of the disease before the first symptoms appear. That would offer an opportunity to identify those at risk and perhaps help in the search for new drug therapies. The research is published in EMBO Molecular Medicine.
One of the hallmarks of Alzheimer’s disease is the accumulation of amyloid-beta plaques in the patient’s brain. The new blood test works by measuring the amounts of two types of amyloid-beta in the brain — a healthy form and a damaging form. The test was developed by Klaus Gerwert and his team at Ruhr University Bochum, Germany.
The pathological form of amyloid-beta is a misfolded version and is known to initiate the formation of toxic plaques in the brain. Toxic amyloid-beta molecules start accumulating in the patients’ body 15-20 years before the disease becomes apparent. In the study, Gerwert and colleagues from Germany and Sweden addressed whether the blood test would be able to pick up indications of pathological amyloid-beta in very early phases of the disease.
The researchers first focused on patients in the early stages of the disease. They found that the test reliably detected amyloid-beta alterations in the blood of participants with mild cognitive impairment that also showed abnormal amyloid deposits in brain scans.
In a next step, the researchers investigated whether they could detect blood changes well ahead of disease onset. They used data from a cohort study that compared blood samples of 65 participants that were later in the follow-up studies diagnosed with Alzheimer’s disease with 809 control subjects.
The test was able to detect signs of the disease on average eight years before diagnosis in individuals without clinical symptoms. It correctly identified those with the disease in almost 70% of the cases, while about 9% of true negative subjects would wrongly be detected as positive. The overall diagnostic accuracy was 86%.
The researchers say their blood test could serve as a cheap and simple option that would pre-select individuals for further testing through brain scans, analysis of cerebrospinal fluid and other more expensive and invasive procedures.
The complete text of the study is available online.