Sniff Test May Signal Disorders’ Early Stages

By ELIZABETH SVOBODA

Seven years ago, Robert Gesteland, a biologist at the University of Cincinnati, and his colleague Robert Frank, a psychologist, decided to tackle a perplexing topic: why some people are more open to trying unfamiliar foods. Suspecting that picky eaters might be more attuned to strong smells, they set about trying to quantify this.
“Someone turned up the suggestion that people might take smaller sniffs once they detect a smell,” Dr. Gesteland said. “It was natural for me to say, ‘How can we measure that? Let me see what I can put together in the garage.’ ”
Since then, the apparatus he built at his home workbench has evolved into a device called the Sniff Magnitude Test — and one the two scientists are using for a much different purpose. As the only test that measures patients’ ability to smell without requiring them to put the sensation into words, it shows promise in helping detect neurodegenerative disorders like Alzheimer’s and Parkinson’s in their earliest stages.
Doctors have known for years that when people with these diseases begin the slide toward dementia, an inability to smell is often the first sign of a problem. Because comparatively few brain cells are devoted to processing odors, “there’s good reason to think the olfactory system is affected very early on with these conditions,” said Richard Doty, director of the University of Pennsylvania’s Smell and Taste Center, who has done research comparing the Sniff Magnitude Test with other smell-assessment measures. “Many patients tell their doctors they can’t smell years before they actually get Alzheimer’s or Parkinson’s.”
The Sniff Magnitude Test, developed with the aid of a $1.3 million grant from the National Institutes of Health, consists of a nasal tube called a cannula attached to a plastic container about the size and shape of a coffee thermos. Chemical vapors inside the canister are released through the tube, exposing subjects to a series of smells, some more objectionable than others.
“People describe some of the smells as skunky or sewerlike,” said Jason Bailie, a University of Cincinnati graduate student working on the test. “There’s also one that smells like banana.”
As patients take whiffs of each new fragrance, sensors in the thermos unit measure the negative pressure the inhalations produce. The size and intensity of these sniffs turn out to be important gauges of olfactory ability. After detecting a strong or disagreeable odor, people with a normal sense of smell take very small sniffs to avoid smelling it. Subjects with an impaired sense of smell, on the other hand, continue taking deep whiffs, because the scent does not register in their brains.
In a study published last year in the journal Otolaryngology, Dr. Frank and Dr. Gesteland reported a high degree of correlation between patients’ scores on the Sniff Magnitude Test and their scores on older smell-assessment tests. The WR Medical Electronics Company in Stillwater, Minn., has started making the device, hoping to begin distribution in the next year.
It will enter a crowded field. Many tests to gauge smelling ability are already available to doctors, including the current gold standard, the University of Pennsylvania Smell Identification Test, which Dr. Doty developed in the 1980s. This test presents patients with 40 squares of paper infused with odors and asks them to choose an accurate description of each smell from four options. Similar tests include the Connecticut Chemosensory Clinical Research Center Test and the “Sniffin’ Sticks” test, which dispenses odors from penlike devices.
But those tests generally ask subjects to relate odors to presumably familiar smells like “dill pickle,” “root beer” and “pumpkin pie,” which may be a challenge for people from other cultures or those whose cognitive abilities are slipping. The Sniff Magnitude Test does not require these kinds of subjective comparisons.
The Cincinnati team’s efforts have piqued the interest of other researchers, including Dr. Doty and Alan Hirsch of the Smell and Taste Research and Treatment Foundation, who is using the Sniff test in his clinical practice. “They’ve chosen some very good odors that stimulate the olfactory system effectively,” Dr. Doty said. “This is a very novel approach — it just needs to be tested more broadly.”
Still, Dr. Doty added, the Sniff Magnitude Test may not be the ideal way to assess every patient with cognitive deficits. “Very early in life, we make a connection between an odor and its source,” he said. “We give it a name. If the connection between the name of an odor and the odor itself is what’s breaking down in an Alzheimer’s patient, this test might not be as helpful,” because it does not tell evaluators how a patient identifies and categorizes smells. The Sniff Magnitude Test is likely to raise red flags only if an impending cognitive disorder directly affects a patient’s olfactory abilities.
Even for patients who fall into this category, the test is no diagnostic panacea. Dr. Gesteland cautions that it should not be used by itself, but in conjunction with more traditional neurological assessments. A poor test result in an older person does not necessarily indicate the presence of Alzheimer’s or Parkinson’s, but it does alert doctors that further investigation is necessary.
“As people get older, their sense of smell can diminish independent of any dementia,” Dr. Gesteland said. “If a patient does poorly, you have to figure out whether the problem is with the nose, with the nerve fibers that go from the nose to the brain, or with how the central nervous system interprets that message.”
Beyond its usefulness as a first-alert mechanism, Dr. Frank thinks the test will help doctors zero in on specific diagnoses. Parkinson’s, for instance, has a clinical profile similar to a condition called progressive supranuclear palsy, but the palsy disorder seldom affects the ability to smell. The test should also help distinguish Parkinson’s and Alzheimer’s from major depression in the elderly, because depressed patients do not experience sensory deficits.
In his most ambitious moments, Dr. Frank envisions doctors administering the Sniff test across the board as patients enter their 50s and 60s. “If folks take this test and some of them don’t do very well,” Dr. Frank said, “we need to be able to refer them.”