Researchers at Ruhr University in Germany have developed a blood test for Alzheimer’s disease and found that it can detect early indicators of the disease long before the first symptoms appear in patients. The research has been published in the journal EMBO Molecular Medicine.
One of the hallmarks of Alzheimer’s disease is the accumulation of amyloid-beta plaques in the patient’s brain. The blood test works by measuring the relative amounts of a pathological and a healthy form of amyloid in the blood. Toxic amyloid-beta molecules start accumulating in the patients’ body 15 to 20 years before disease onset.
In the present study, the researchers looked at whether the blood test would be able to pick up indications of pathological amyloid-beta in very early phases of the disease.
They 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.
They then investigated if their test was able to detect blood changes well ahead of disease onset. Using data from the ESTHER cohort study, the researchers compared blood samples of 65 participants that were later in the follow-up studies diagnosed with Alzheimer’s disease with 809 controls. 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 per cent of the cases, while about 9 per cent of true negative subjects would wrongly be detected as positive. The overall diagnostic accuracy was 86 per cent.
Currently available diagnostic tools for Alzheimer’s disease either involve expensive positron emission tomography (PET) brain scans, or biopsies of cerebrospinal fluid extracted via lumbar puncture.
In the future, the researchers say, their blood test will be extended to Parkinson disease by measuring another disease biomarker (alpha-synuclein) instead of amyloid-beta.