CHICAGO – A test to detect those likely to develop Alzheimer's disease before symptoms appear finally may be on the horizon after scientists found changes in spinal fluid can predict the disease with 90 percent accuracy nearly a decade before dementia sets in.
A study tracking the progress of a group of patients over an average of nearly 10 years found those who already had mild thinking difficulties as well as lowered levels of a beta-amyloid protein in their cerebro-spinal fluid at the start of the study were overwhelmingly likely to progress to Alzheimer's by the end.
The findings, published Tuesday in the journal Archives of General Psychiatry, were described by an Australian expert as "a bit of a breakthrough" for offering the most promising sign yet that an accurate test might be available in coming years.
Alzheimer's, the most common form of dementia, accounting for up to 70 percent of cases, is currently diagnosed only after patients become demented.
While the ability to detect the disease earlier would at present be of limited use, because doctors have few effective treatments, the study's authors said this was expected to change over the coming decade.
As the treatments were likely to have the greatest benefit in the earliest stages of the disease, before symptoms became severe, a test that could identify those likely to be affected would become highly useful.
As well as lowered levels of a subtype of beta-amyloid that is prone to aggregating into the sticky plaques seen in the brains of affected patients, the patients who developed Alzheimer's also showed changes in two other proteins, called T-tau and P-tau.
The study's authors, from Sweden's Lund University in Malmo, Skane University Hospital in Malmo and the University of Gothenburg, said the research suggested about 90 percent of patients who had both mild cognitive impairment and the tell-tale changes in spinal fluid composition would develop Alzheimer's within 9.2 years.
"Therefore, these markers can identify individuals at high risk for future AD [Alzheimer's disease] at least five to 10 years before conversion to dementia," they wrote.
"Hopefully, new therapies that can retard or even halt progression of the disease will soon be available. Together with an early and accurate diagnosis, such therapies could be initiated before neuronal degeneration is too widespread and patients are already demented."