Many scientists are working to develop tests that can reliably diagnose Alzheimer’s disease and predict its course in order to make it possible to screen people who will suffer from this disease before they show symptoms.
Researchers from Emory University, Atlanta, presented on Wednesday, September 6, in Science Translational Medicinethe test they designed that increases the reliability of the prediction.
Doctors usually diagnose Alzheimer’s in people who begin to show symptoms using about 30 questions that measure their cognitive abilities. The reliability of the diagnosis obtained in this way is about 80%, underlines the Dr Judes Poirier, who is director of the Molecular Neurobiology Unit at the Douglas Research Center.
To increase the accuracy of the diagnosis, some neurologists will take cerebrospinal fluid by lumbar puncture – in which the brain and spinal cord bathe – in order to measure the concentration of three molecules which are abnormally abundant in the brains of people with AD. alzheimer. “Detecting these three disease markers of beta-amyloid 42, total tau and phospho-tau 181 allows us to screen people who will develop Alzheimer’s in the relatively near future with a reliability of order of 90%”, specifies the Dr Poirier, who is a professor in the Department of Psychiatry at McGill University.
The test presented by Emory University researchers involves taking cerebrospinal fluid, in which they look for 48 other molecules that appear to be abnormal in people with Alzheimer’s.
Their test, which they tested in individuals at different stages of the disease, some of whom were still asymptomatic, allows a diagnosis with an accuracy of 94%.
“It’s a gain [de 4 %] and the choice of molecules is entirely justified on the basis of our knowledge of the emergence of the disease. But this test requires a very sophisticated technology which requires a large quantity of samples, which is complex and very expensive, and which, therefore, does not really lend itself to the clinic”, says Dr.r Poirier, who is a little disappointed by the performance of the test, which only increases the accuracy of disease predictability by 4%.
The Emory University team is one of a dozen different groups around the world working to develop a method that would allow early diagnosis to be made with high reliability. It is therefore a very dynamic subject of research, since detecting the disease early would make it possible to delay the onset of symptoms through early treatment.
The silent phase of the disease, which precedes symptoms, is estimated to last between 20 and 30 years, while the symptomatic phase lasts between 8 and 11 years. “This means that we are two-thirds of the way through when the symptoms appear. It is clear that any significant biological change does not occur only when symptoms appear. The two decades preceding the expression of the disease are therefore the most strategic,” notes Dr.r Poirier.
“One day, we will no longer wait for symptoms to appear to treat someone. People who are on an Alzheimer’s trajectory in their 40s and 50s will be identified, and treatment will begin right away to delay the disease long enough for people to die of old age or other conditions than death. Alzheimer’s disease”, continues this great Alzheimer’s specialist.
The D teamr Poirier is also working on the design of a more reliable diagnostic test. She looked at 291 molecules that seemed to be involved in Alzheimer’s. “Our test increases accuracy over using all three markers, but not dramatically. However, we discovered that a dozen of these molecules had a much more elaborate biological role than we had imagined. Each of these molecules is the subject of research in my laboratory, because determining their role, their precise contribution to the disease will help us to better understand the causes of Alzheimer’s,” says the researcher.
“One of these molecules — which is abnormally expressed (that is, too abundant) 10 to 15 years before the onset of symptoms — is associated with insulin. She comes to get the insulin once it has finished its action and she brings it to be degraded, “says the Dr Poirier.
The latter was not surprised to find an abnormality in insulin, because diabetes is a major risk factor for Alzheimer’s disease. “Uncontrolled diabetes doubles, or even triples, the risk of one day suffering from Alzheimer’s,” he warns.
“When you meet the children of people [souffrant ou ayant souffert d’alzheimer] and who are therefore at risk because of their family history, we check whether they have diabetes, hypertension and high cholesterol, which are three important risk factors after those of ‘age [avancé] and sex [les femmes sont deux ou trois fois plus à risque que les hommes]. As we have multiple molecules to control hypertension, cholesterol and diabetes, we can reduce their risk of developing Alzheimer’s by managing these three factors,” he says.
Obviously, we are finally making progress in the prevention of this proliferating disease.
