A new study led by Lund University in Sweden has found that a blood test can accurately identify Alzheimer’s disease in Down syndrome patients.

In the study, which was published in JAMA Neurology, a blood biomarker was compared with PET imaging results to find whether people had significant amounts of proteins, such as tau and amyloid aggregates, that can indicate Alzheimer’s disease accumulated in the brain.

It involved 300 Down syndrome patients, with 40% showing signs of Alzheimer’s disease onset.

In 2020, Lund University Clinical Memory Research Unit Neurology professor Oskar Hansson and his research team announced that a biomarker, phosphorylated tau (P-tau217), in the blood could detect Alzheimer’s disease as early as 20 years before memory impairment was noticeable.

Down syndrome patients have an extra chromosome, specifically three copies of chromosome 21 instead of two.

Chromosome 21 is the home of the amyloid precursor protein (APP) gene, which produces amyloid.

Lund University researcher Shorena Janelidze said: “Down syndrome produces more of the APP protein and thus results in a significantly increased risk of amyloid aggregates, which in turn lead to tau aggregates.”

The study used blood samples and Down syndrome patients’ PET scan results to examine whether the biomarkers could work as a diagnostic marker to detect Alzheimer’s in people with Down syndrome.

Janelidze further added: “Our results show that P-tau217 works just as well as a blood marker of Alzheimer’s disease for persons with Down syndrome as it does for others and that other blood markers are not needed, Ptau217 is sufficient.

“The next step is to evaluate the performance of this biomarker in clinical practice and use it to improve clinical trials evaluating drugs targeting Alzheimer’s disease in people with Down syndrome.”

Clinical trials, which will include cognitive evaluation and P-tau217 measurements in blood, are currently being conducted at 25 health centres in Sweden.