To confirm a diagnosis of Alzheimer's today, a patient either needs a painful spinal tap or a costly brain image. But several detection tools under development offer the promise of at least ruling out Alzheimer's easily and inexpensively in a doctor's office.
In new research to be presented this week at the Alzheimer's Association International Conference in Denmark, scientists show progress developing detection methods that rely on the blood, sense of smell and protein build-up in the eyes. All have been tested in dozens to hundreds of patients.
"Those are now moving into the more serious realm," said Maria Carrillo, vice president of medical and scientific relations for the Alzheimer's Association. "So we're very excited about this."
Among people with mild memory problems, a reduced sense of smell effectively predicted who would go on to get Alzheimer's, according to one study to be presented today. Also, older, healthy people were more likely to have memory declines if they scored lower on a smell test, said Davangere Devanand, a psychiatrist and director of the division of geriatric psychiatry at Columbia University.
Other studies include one suggesting that a device the size of a desktop computer can detect Alzheimer's by looking at the lens of a patient's eye. Beta amyloid, a protein that builds up in the brains of Alzheimer's patients, is detectable in the lens, potentially before symptoms appear, said Paul Hartung, president and CEO of the Massachusetts-based company Cognoptix that is developing the device.
And in another study reported recently, researchers at King's College London and UK proteomics company, Proteome Sciences, found that a panel of 10 proteins in the blood can help identify people with the brain shrinkage that is characteristic of mild memory loss and Alzheimer's.
None of these tests is likely to be perfect predictors of Alzheimer's, though, said Ralph Nixon, chairman of the Alzheimer's Association's Medical & Scientific Advisory Council, and a professor of psychiatry and cell biology at New York University School of Medicine. Everyone with Alzheimer's has beta amyloid in their brain, but not everyone with beta amyloid buildup will develop Alzheimer's, limiting the predictive ability of some of these tests.
Their best use may be to help flag people who need costlier testing, or to quickly rule out Alzheimer's as a cause of symptoms, said Devanand, who does not expect the smell test to be definitive.
The other long-term hope is that these sensory and blood tests may be able to predict Alzheimer's risk long before symptoms appear. In recent years, trials of drugs to change the course of Alzheimer's have all been failures. Researchers believe that's because the drugs are given after too much damage has occurred – but right now, they can't identify the disease any earlier.
Earlier diagnosis offers the possibility of treating people sooner, when medications may be more effective, said Matthew Growdon, a medical student at Harvard Medical School and the Harvard School of Public Health. At the conference Growdon will also present research on the link between odor identification and the biological characteristics of Alzheimer's.
The smell test is a 15 to 20 minute quiz in which the participant has to scratch and sniff one box at a time and identify its odor from among four options such as pizza, gasoline, apple and chocolate. The scents are intentionally different because many people would have trouble with more subtle distinctions – say, between and apple and a strawberry. And, the test is meant to be easy, Devanand said.
By itself, a lousy sense of smell doesn't predict Alzheimer's – so people shouldn't worry if they don't discern smells as well as a family member, Devanand said. Respiratory infections, allergies, smoking and other factors can all reduce smelling ability.
"It is not as if, if you score poorly, you are sure to have Alzheimer's," he said.