Alzheimer's Blood Test From Lund University Shows High Diagnostic Accuracy

Alzheimer's disease diagnosis remains difficult

Human brains are bound to falter. Working out whether worsening memory signals something beyond normal ageing needs technology that is not always accessible, so specialists may have to depend entirely on their own expertise and judgement to recognise possible dementia.

Scientists have now established that a blood test already available clinically can complement existing diagnostic approaches when costly scans and spinal-fluid samples cannot be used. It also seems to offer very high accuracy.

A research team led by Lund University in Sweden assessed whether combined ratios of proteins in human serum could reliably identify Alzheimer's pathology in patients.

Around 55 million people worldwide are living with dementia, with Alzheimer's disease accounting for most cases.

Although the underlying processes result from a complex combination of genetic and environmental influences, every person with Alzheimer's experiences an ongoing loss of vital neurons alongside a substantial increase in abnormal proteins.

The two proteins, beta-amyloid and tau, form clumps and tangles that can either harm cells directly or trigger damage through other immune processes.

Blood test compared with established assessments

GPs and specialists commonly combine CT scans, which can show this loss of brain tissue, with cognitive assessments and patients' own reports of symptoms to judge whether Alzheimer's disease is probable.

Even under ideal circumstances, with the complete range of diagnostic tools available, clinicians in both primary and secondary care frequently do not reach the correct conclusion.

"Primary care doctors' accuracy in identifying Alzheimer's disease was 61 per cent, while specialist physicians were correct 73 per cent of the time," says Lund University neurologist Sebastian Palmqvist.

"This underscores the lack of good, cost-effective diagnostic tools, particularly in primary care, and indicates the potential improvement in diagnosis with the adoption of this blood test in healthcare settings."

A number of studies in recent years have pointed to the possible value of plasma-protein measurements for diagnosing Alzheimer's disease, particularly ratios comparing the 'normal' and abnormal forms of beta-amyloid and tau.

Although comparable tests have been performed using spinal fluid, a commercially available blood test would be much less invasive and painful, as well as faster to undertake in an ordinary clinic.

To determine whether the blood test was equally dependable, Palmqvist's team enrolled 1213 patients being assessed for Alzheimer's by either their GP or a specialist in Sweden between February 2020 and January 2024.

About two-thirds had been identified as having subjective cognitive decline or mild cognitive impairment. The other third had already been diagnosed with dementia using a combination of clinical and cognitive assessments.

Lund University study results and availability

Alongside the blood test, most participants underwent a lumbar puncture to collect spinal fluid. The small number unable to have this procedure received a radionuclide-tagged PET scan instead, to examine abnormal protein build-ups in the brain.

When the findings were compared, the two assessment methods performed equally well, each predicting Alzheimer's with a 90 percent accuracy.

Because blood testing is more convenient, a greater number of patients could obtain an accurate diagnosis earlier and access the healthcare they need without unnecessary delay.

"The test is already available in the USA and is likely to become available in many other countries soon," says senior researcher Oskar Hansson, a neurologist at Lund University.

"Initially, it will mainly be used in specialist memory clinics, and it may take approximately one to two years to implement guidelines and training in primary care."

The research was published in JAMA.