A proof-of-concept study by a team of Lund University scientists shows that their brief, self-administered digital cognitive test — named BioCog — can detect cognitive impairment and, when combined with a blood test, accurately identify clinical Alzheimer’s disease in primary care.
In primary care, the BioCog test had an accuracy of 85% when using a single cutoff to define cognitive impairment, which was significantly better than the assessment of primary care physicians (accuracy 73%). Image credit: Miroslaw Miras.
Alzheimer’s disease is the most common cause of dementia, characterized by depositions of amyloid-beta, aggregated tau and progressive neurodegeneration.
The clinical syndrome of Alzheimer’s disease typically starts with subjective cognitive decline, in which individuals report memory problems and/or other cognitive difficulties but perform normally on cognitive tests.
This phase is followed by mild cognitive impairment, marked by objective cognitive symptoms, and later by dementia, characterized by clear functional deficits in activities of daily living.
Diagnosing Alzheimer’s disease is challenging, especially in the early stages of the disease and in primary care.
The prevalence of both underdiagnosis and misdiagnosis is high with 20-30% of people being misdiagnosed in specialized care and approximately 40% in primary care when the Alzheimer’s diagnosis is not supported by biomarkers.
“The BioCog digital test, which patients perform on their own with minimal involvement from healthcare personnel, improves the primary care physician’s ability to determine who should be further examined by blood tests for Alzheimer’s pathology early in the investigation phase,” said Lund University’s Professor Oskar Hansson
“Primary care does not have the resources, time or specialist knowledge to investigate possible Alzheimer’s disease in the same way as specialised memory clinics.”
“And this is where a digital cognitive test can make the biggest difference.”
Unlike pen-and-paper tests, which are generally used to assess cognitive impairment, digital tests provide a more detailed picture.
More aspects and new variables that could not previously be measured as easily are included.
“The vast majority of people who experience memory loss will first seek treatment at their health center,” said Pontus Tideman, doctoral student at Lund University and psychologist at the Memory Clinic, Skåne University Hospital.
“Our new digital test provides a first objective picture — at an earlier stage and with greater precision — of which patients have cognitive impairment indicative of Alzheimer’s disease.”
“This indicates who should proceed with the blood test that measures the level of phosphorylated tau and is able to detect Alzheimer’s pathology in the brain with high accuracy.”
At the moment, these blood tests are only available in specialised clinics/memory clinics in hospitals.
In the long term, they will also be available in primary care, but doing blood tests on all patients presenting with cognitive problems is not the intention.
The researchers believe that the digital tool could be of great benefit, as it is currently very challenging to diagnose Alzheimer’s disease during a 15 to 20-minute patient encounter.
This is where digital tools, which measure cognitive skills in an objective way, can make a big difference.
“The unique aspect of our BioCog test is that unlike other digital tests, it has been evaluated in a primary care population, i.e. patients seeking treatment at a health center because they are experiencing cognitive problems, such as memory problems,” said Linda Karlsson, a doctoral student ay Lund University.
“Combining the results of the digital test and the blood test increases the accuracy of diagnosing Alzheimer’s disease.”
“The purpose of the test is to make things easier for primary care doctors.”
The BioCog test is described in a paper in the journal Nature Medicine.
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P. Tideman et al. Primary care detection of Alzheimer’s disease using a self-administered digital cognitive test and blood biomarkers. Nat Med, published online September 15, 2025; doi: 10.1038/s41591-025-03965-4
