A research group in Boston recently used an olfactometer to determine the early diagnosis of Alzheimer's disease, and they published the results of this study in the recent issue of Annals of Neurology. Those in the Alzheimer's disease community have been aware for many years of the deficits in olfactory function early in the disease process. The olfactory system is also impacted in Parkinson's disease.

But testing of olfactory deficits can be cumbersome and difficult to interpret. The research led by Mark W. Albers, M.D., Ph.D., assistant professor of neurology at Mass General Institute for Neurodegenerative Disease, addressed many of the confounding issues that research into smell presents.

"People's ability to identify and detect odors varies greatly, and that's partly due to genetics of the olfactory receptors you inherit, the structure of your nose and how you process olfactory information," Albers told the Boston Herald. "We are taking those things into account."

There are several clinical tests of olfaction that are available, including a Sniffnsticks Test that has several pen-like vials and a Brief Smell Identification Test (BSMIT) that includes a set of strips. The olfactometer used for the Alzheimer's disease research utilizes 10 common scents, including menthol, clove, leather, strawberry, lilac, pineapple, smoke, soap, grape or lemon during the first phase of the test. After the first phase of identification the test, the same 10 scents are intermixed with 10 more: banana, garlic, cherry, baby powder, grass, fruit punch, peach, chocolate, dirt and orange.

During the second phase of the test, a patient would not only identify what the scent is, but report whether it had been part of the 10 in the first phase of testing. The additional memory testing in the second phase was shown to be better at identifying those with Alzheimer's disease and those with early signs of dementia.

The research looked at 183 patients, and plans are underway to test another 140. The researchers also had a battery of questions related to scents and the patients' history and emotional response to odors.

The hope of using such simple test of olfaction is the early identification of those with Alzheimer's disease.

"There is increasing evidence that the neurodegeneration behind Alzheimer's disease starts at least 10 years before the onset of memory symptoms," Albers said. "The development of a digitally-enabled, affordable, accessible and noninvasive means to identify healthy individuals who are at risk is a critical step to developing therapies that slow down or halt Alzheimer's disease progression."

Having a test that is predictive and sensitive is also a means to keep the costs of an early diagnosis down. An inexpensive and comprehensive screening would better predict who should go on to have the more expensive tests such as brain imaging.