'Scratch 'n' sniff' test may reveal early Parkinson's.
Olfactory loss, a well-accepted symptom of Parkinson's disease, may occur before onset of motor symptoms. Therefore, impaired olfaction could be a clinical marker to assist early diagnosis and treatment. Researchers aimed to determine the sensitivity and specificity of screening with the "scratch 'n' sniff" test alone versus in combination with specific neuroimaging, Danna L. Jennings, M.D., said during an interview at her poster presentation.
"We asked community neurologists to send us cases they were unsure about. We're trying to develop a good screening battery that is noninvasive, inexpensive, and easy to administer," said Dr. Jennings, clinical research director at the Institute for Neurodegenerative Disorders in New Haven, Conn.
Dr. Jennings and her associates screened 112 patients with suspected Parkinsonian syndrome using a 40-item multiple-choice olfactory test. A total of 84 patients completed the study. The mean age was 62 years.
A majority, 70%, had abnormal olfaction, defined as a score below the 25th percentile on the University of Pennsylvania Smell Identification Test (UPSIT) according to age and gender. Baseline dopamine transporter imaging (DAT) yielded suspicious findings for early Parkinson's disease in 58% of all participants. DAT imaging was considered positive for Parkinsonian syndrome in cases that had a reduction in [[.sup.123]I][beta]-CIT uptake of 30% when compared with a healthy control database of 93 individuals. A movement disorders expert blinded to DAT imaging results performed a clinical examination of each participant.
The sensitivity and specificity of UPSIT screening alone and combined UPSIT/DAT screening were determined by comparison to a clinical follow-up examination at 6 months and 12 months. "Ultimately, Parkinson's disease reveals itself over time," Dr. Jennings said.
DAT imaging alone has 94% sensitivity and 92% specificity. The UPSIT alone has 85% sensitivity and 46% specificity. "It's not very specific, there are a lot of things--head injury, nasal injury, Alzheimer's disease--that can affect the sense of smell," Dr. Jennings said. An abnormal UPSIT followed by a DAT scan is 96% sensitive and 86% specific, "putting us closer to imaging alone, at a lot less expense."
Initial screening with the olfactory test to guide follow-up DAT imaging could save substantial money compared with imaging all patients with suspected early disease. A DAT scan costs between $1,500 and $2,000, versus about $30 for the UPSIT scratch 'n' sniff test, Dr. Jennings said.
"These pilot data suggest that olfactory identification testing may serve as an easily administered and relatively sensitive tool to assess for early Parkinson's disease," the authors wrote. Using the UPSIT in combination with DAT imaging, which is a highly specific test for Parkinsonian syndrome, offers the potential to screen large populations in a practical fashion."
The researchers plan to study other screening tools--such as a limb kinematic test, cognitive test, or depression questionnaire--to improve the specificity of the olfactory test. The ultimate goal is to develop an easy-to-administer, highly predictive test for early Parkinson's disease that could be used in primary care or even as a self-administered test, Dr. Jennings said.
BY DAMIAN MCNAMARA
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|Publication:||Internal Medicine News|
|Date:||May 15, 2005|
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