Smell Test for Accuracy in Alzheimer’s Diagnosis

Diagnosis of Alzheimer’s disease remains a challenge for doctors, who rely on a combination of mental and physical examinations to detect the condition. In a new study, researchers describe how a smell test could enhance the accuracy of an Alzheimer’s diagnosis.

Principal investigator David R. Roalf, Ph.D. - an assistant professor in the Department of Psychiatry at the University of Pennsylvania School of Medicine - recently reported new findings in the Journal of Alzheimer’s Disease.

Alzheimer’s disease is a neurological disorder characterized by memory problems and changes in behavior. It is the most common form of dementia, accounting for around 60-80% of all dementia cases in the United States.

At present, there is no single test for Alzheimer’s. Doctors make a diagnosis through a series of assessments, including physical and neurological examinations, mental state tests, blood tests, brain imaging, and an evaluation of medical history.

Previous studies have suggested that sense of smell diminishes with Alzheimer’s; as such, researchers have increasingly investigated whether a sniff test could be used to detect the disease, reports medicalnewstoday.com.

A study in November revealed how a series of olfactory tests effectively pinpointed patients with Alzheimer’s, and researchers found that patients with a reduced sense of smell were more likely to have brain abnormalities associated with the disease.

The new study from Roalf and team offers support to such research, after finding that a sniff test boosted the diagnostic accuracy for Alzheimer’s disease and mild cognitive impairment (MCI), which is considered a precursor to Alzheimer’s.

To reach their findings, Roalf and colleagues enrolled 728 older adults, of whom 292 were healthy, 262 had Alzheimer’s disease, and 174 had MCI.

Participants’ sense of smell was tested using the Sniffin’ Sticks Odor Identification Test (SS-OIT), which required them to identify 16 different odors. Subjects also underwent standard cognitive testing.

Researchers assessed the accuracy of cognitive testing alone for the diagnosis of Alzheimer’s and MCI, as well as in combination with the SS-OIT. The team found that the SS-OIT significantly increased diagnostic accuracy for patients; cognitive testing alone diagnosed MCI with 75% accuracy, but this increased to 87% when SS-OIT was included.

Similar results were seen for the diagnosis of Alzheimer’s disease, and the team says that the SS-OIT even helped to identify which patients had more advanced forms of MCI.

“We’re hoping to shorten the Sniffin’ Sticks test, which normally takes 5 to 8 minutes, down to 3 minutes or so, and validate that shorter test’s usefulness in diagnosing MCI and dementia - we think that will encourage more neurology clinics to do this type of screening,” says Roalf.