A blood biomarker can detect Alzheimer’s disease in adults with Down syndrome

The Alzheimer – Down Unit, that comprises researchers from the Sant Pau Memory Unit of the Neurology Service at Hospital de la Santa Creu i Sant Pau and the Fundació Catalana Síndrome de Down, has published the results of a study of biomarkers in blood and cerebrospinal fluid of adults with Down syndrome in the prestigious journal The Lancet Neurology.

The aim of the study was to assess the usefulness of these biomarkers in diagnosing Alzheimer’s disease in this population. Alzheimer’s disease has become the main medical problem for the adult person with Down syndrome. The prevalence of dementia in this population increases exponentially from 40 years to over 80% in those over 60 years.

Blood and CSF biomarkers in Down Syndrome - Sant Pau Memory Unit - Alzheimer Research - Barcelona

What was done in this study?

To carry out this study, donation of blood samples was requested to 282 people with Down syndrome of the DABNI project (Down Alzheimer Barcelona Neuroimaging Initiative). Of these, 94 also accepted a lumbar puncture for the analysis of cerebrospinal fluid. Blood and cerebrospinal fluid samples from 67 volunteers without Down syndrome from the SPIN cohort (Sant Pau Initiative on Neurodegeneration) were also included in the study.

All participants were evaluated neurologically and performed neuropsychological tests that allowed their classification according to the degree of cognitive and functional impairment. Blood and cerebrospinal fluid samples were analyzed to determine the levels of the Aβ42, Aβ40, tau and NfL proteins.

Main results

This work has revealed that, both the conventional biomarkers of Alzheimer’s disease in cerebrospinal fluid (protein Aβ amyloid, tau-total and phospho-tau), and plasma levels of protein NfL (Neurofilament Light protein) have very good performance for an early diagnosis of the symptoms of this disease. The results support the use of plasma NfL levels as an easily accessible and relatively inexpensive biomarker for diagnosing the symptoms of Alzheimer’s disease.

Relevance of the study

This could mark a paradigm shift in the diagnosis of Alzheimer’s disease, which at this time is very complex due to the variability of the degree of intellectual disability among this population and the lack of validated useful neuropsychological tests. The use of these biomarkers will allow an earlier and more accurate diagnosis of the disease. Also, this study could have a direct impact on the design of clinical trials of prevention in people with Down syndrome, which are currently very limited due to the difficulty to standardize the onset of symptoms of Alzheimer’s disease in this population.

To date, this is the study of biomarkers that includes a greater number of participants with Down syndrome. For the first time, biomarkers of Alzheimer’s disease in cerebrospinal fluid of people with Down syndrome are characterized, something that until now had only been studied in series of very small cases. Researchers have confirmed that the behaviour of these biomarkers is similar to that of the general population, supporting the idea that the study of Alzheimer’s disease in Down syndrome would not only be very useful for this population, but can also contribute novel information applicable to the general population.

Also for the first time, SIMOA (Single Molecule Array), an ultrasensitive technology with greater precision than conventional laboratory tests, has been used to determine plasma biomarkers. It is also the first time that the relationship between biomarkers in cerebrospinal fluid and plasma in Down syndrome has been studied.

More information

This work has been funded by several competitive projects of the Instituto de Salud Carlos III and La Marató Foundation of TV3, the Fundació Obra Social la Caixa, the Fundació Catalana Síndrome de Down and the Fundació Victor Grifols i Lucas.

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