A newly developed blood test may offer a fast, accurate, and cost-effective means of diagnosing Alzheimer’s disease (AD), even in patients who have not yet started experiencing symptoms.

By analyzing plasma levels of certain proteins strongly associated with the condition, the test allows early detection of AD without the need for expensive and invasive procedures. This could lead to the development of routine screening protocols to catch the illness in its earliest stages.

“A blood test for Alzheimer’s provides a huge boost for Alzheimer’s research and diagnosis, drastically cutting the time and cost of identifying patients for clinical trials and spurring the development of new treatment options,” explained lead author Randall J. Bateman in a statement.

“As new drugs become available, a blood test could determine who might benefit from treatment, including those at very early stages of the disease.”

Alzheimer’s is at least partially caused by the build-up of amyloid protein plaques in the brain. At present, these can only be accurately diagnosed using highly expensive PET scans or invasive spinal taps, yet the new blood test may eliminate the need for such procedures by assessing the levels of two key amyloid proteins in the blood.

Appearing in the journal Neurology, the new study describes how the researchers applied the test to blood samples collected from 465 individuals taking part in separate AD trials in the US, Sweden, and Australia. Of these, 46 had been diagnosed with AD following PET scans and cerebrospinal fluid (CSF) assays, while a further 203 had mild cognitive impairment.

Crucially, the researchers noted, “consistent correspondence” between the plasma amyloid levels detected by their blood test and those seen in the PET and CSF analyses. When combined with genetic risk factor assessments, the blood test was 88 percent as accurate as brain scans and 93 percent as accurate as spinal taps at detecting AD.

This accuracy was maintained for patients experiencing cognitive decline and those with no symptoms, suggesting that the method could be used to diagnose AD in individuals who have not yet begun to show signs of it.

According to the study authors, screening with the blood test could enable rapid detection of AD at a fraction of the cost of current diagnostic procedures.

“Our study shows that the blood test provides a robust measure for detecting amyloid plaques associated with Alzheimer’s disease, even among patients not yet experiencing cognitive declines,” said Bateman.

“These results suggest the test can be useful in identifying nonimpaired patients who may be at risk for future dementia, offering them the opportunity to get enrolled in clinical trials when early intervention has the potential to do the most good.”