[The researchers using the test] accurately detected Alzheimer's in 90 percent of patients with the disease. They were also able to detect 100 percent of people with memory impairments who would progress to Alzheimer's disease within five years. And they detected Alzheimer's proteins in 36 percent of people with normal brain function.
[They] analyzed spinal fluid from 114 adults with normal brain function, 200 who had mild cognitive impairment -- a precursor to dementia -- and 102 who had Alzheimer's. They identified one protein signature that was associated with Alzheimer's, and another that indicated healthy brain function.
When they looked to see how accurate these signatures were at spotting the disease, they found 90 percent of those with Alzheimer's had the disease pattern in their spinal fluid. The pattern was present in 72 percent of those with mild cognitive impairment and 36 percent of those who were normal.
The indicators in the healthy subjects may end up being more than coincidental. There have been indications in other research that neurological diseases including Alzheimer's disease can take decades to manifest. I wouldn't be at all surprised if most of the non-symptomatic control group members with the spinal fluid indications of Alzheimer's disease go on to develop that condition.