Screening tests are being developed for early detection of developing Alzheimer’s disease to allow people at risk to receive treatment early before it is too late.
One of the reasons cited by the scientific community for the high failure rate of clinical studies is that it is virtually impossible to treat patients once symptoms are present.
Screening for Alzheimer’s disease by detecting amyloid in the blood
Researchers have developed blood tests that identify the amyloid protein in its abnormal form.
The abnormal shape of the protein is characterized by a modification of its structure which ends up aggregating. This abnormal buildup of amyloid appears about 17 years before symptoms of dementia occur.
This screening test has a reliability of just over 90% when combined with age or the presence of the APOE epsilon 4 allele (APOE4), a genetic risk factor (in 9 cases out of 10, a positive test is confirmed later).
The test would make it possible to identify people at risk of developing Alzheimer’s disease and to refine the diagnosis by lumbar puncture or by positron emission tomography.
Source: Wolters FJ et al. Hemoglobin and anemia in relation to dementia risk and accompanying changes on brain MRI, Neurology, July 2019; A. Nabers et al. Amyloid blood biomarker detects Alzheimer’s disease.EMBO Molecular Medicine (2018) e8763.
Antibodies as screening tools for early detection of Alzheimer’s disease
In 2016, another team used antibodies as biomarkers to detect people with mild cognitive impairment, a stage leading to Alzheimer’s disease but also to other pathologies such as vascular diseases.
The researchers selected 50 antibodies produced by the immune system as being most likely to detect the disease.
They then tested them on 236 people, 50 of whom had mild cognitive impairment.
According to the experiments carried out, the test made it possible with 100% accuracy to determine people with mild cognitive impairment leading to Alzheimer’s disease.
These results must be confirmed before the test is put on the market.
Source: Alzheimer’s & Dementia: Diagnosis, Assessment & Disease Monitoring, 2016.
Early detection of Alzheimer’s disease-specific proteins
In a study published in 2014, a blood test identified 10 disease-specific proteins. 1,148 individuals participated in this study, of which 476 of them had Alzheimer’s disease, 220 had mild cognitive impairment and 452 were in good cognitive health. Of the thousands of proteins found in the blood, 26 have been linked to Alzheimer’s disease, and 16 to brain atrophy (reflecting loss of neurons).
“We have 10 proteins that can predict whether a person with mild cognitive impairment will develop Alzheimer’s disease one year later, with a high level of reliability (87%),” says the study’s lead author.
This test would be used to identify patients at a very early stage of the disease and include them in new clinical trials, in order to increase the chances of developing effective treatments capable of slowing down or even stopping the progression of the disease.
“The next step will be to confirm these results and develop a reliable screening test for Alzheimer’s disease that can be easily used by doctors,” concludes the group of researchers.
Source: Abdul Hye et al. Plasma proteins predict conversion to dementia from prodromal disease. Alzheimer’s & Dementia, July 2014.
Some lipids would also be good indicators
A team of American researchers (Georgetown University) evaluated a test in adults in their seventies in good mental health. They measured the levels of 10 lipids in their blood.
Measuring the levels of these lipids makes it possible to identify, with 90% reliability, those who will develop cognitive impairment over a period of two to three years.
This means that in 9 out of 10 cases, a person with a positive test will suffer from mild cognitive decline or Alzheimer’s disease.
The main author of this research recalls that blood tests are much easier to perform than current tests that involve neuroimaging techniques or cerebrospinal fluid sampling.
The study followed, for 5 years, 525 participants in their 70s in good health, of whom 74 participants were diagnosed with Alzheimer’s disease or amnesic mild cognitive impairment.
Source: Medicine Plasma phospholipids identify antecedent memory impairment in older adults. Nature, March 2014.
A test using DNA
German researchers are planning to develop a blood test for early detection of Alzheimer’s disease.
They identified 12 fragments of microRNA* (or micro ribonucleic acid) which would be characteristic of Alzheimer’s disease.
MicroRNAs are short pieces of RNA that regulate gene expression. As a reminder, RNA is produced from DNA in cells to make proteins.
The reliability of the test is 93%, that is, 93% of the positive screens were found to be accurate.
202 blood samples were analyzed. This blood test will have to be validated with a larger sample.
. Source: Genome Biology journal, July 29, 2013.
Neuroimaging for screening for early detection of Alzheimer’s disease
Swiss researchers have deciphered how different areas of the brain interact with each other in healthy subjects (September 2015).
Using the technique of neuroimaging, they identified thirteen main networks that activate in the brains of these participants. This activation takes place with certain coordination.
These results could have an impact on the detection of Alzheimer’s disease, knowing that it is characterized by a disruption of neural networks located in certain parts of the brain, before the appearance of the first symptoms.
Eye examination
Scottish computer scientists (University of Dundee) will develop, in the spring of 2015, software called VAMPIRE (Vessel Assessment and Measurement Platform for Images of the Retina) which will take images of the vascularization of the eye.
This imaging data will be combined with medical information to establish a possible link between abnormalities in the vessels that irrigate the eye and the onset of Alzheimer’s disease.
The researchers point out that the blood circulation (veins and arteries) of the eye undergoes branching changes following the appearance of certain pathologies such as stroke or cardiovascular disease.
These abnormalities of the vascular system are characterized by a change in the morphology of the vessels, which become wider and more sinuous. They can be the beginnings of Alzheimer’s disease.
In 2014, Cognoptix, an American biotechnology company, developed an eye examination device (SAPPHIRE II) to achieve early detection of Alzheimer’s disease.
This examination would make it possible to identify a biological marker characteristic of the disease (in this case amyloid) by examining the eyes of patients, according to Carl Sadowsky, principal coordinator of clinical trials.
These studies involved 20 healthy volunteers and revealed that this test has a sensitivity of 85% and a specificity of 95% when it comes to distinguishing patients at risk from those who are not affected.