Olfactory testing in consecutive patients referred with suspected dementia

Area of Science:

• Neurology
• Geriatrics
• Neuroscience

Background:

• Alzheimer's disease (AD) is the leading cause of dementia, making early diagnosis crucial.
• Olfactory dysfunction is recognized as an early indicator of AD.
• The utility of olfactory testing in diagnosing AD among unselected patients with suspected dementia requires further investigation.

Purpose of the Study:

• To evaluate the effectiveness of olfactory testing in identifying probable AD.
• To assess the role of smell tests in the diagnostic workup of patients with suspected dementia.

Main Methods:

• A two-step study was conducted, beginning with a comparative analysis of healthy controls and probable AD patients.
• The second step involved a blinded study of consecutive patients referred to a geriatric clinic for suspected dementia.
• Olfactory function was assessed using a scent detection test.

Main Results:

• The olfactory test effectively distinguished probable AD patients from controls in the initial study (AUC=0.94).
• In the blinded study, olfactory testing showed an odds ratio of 12 for probable AD with two or more smell errors (p=0.026).
• The test demonstrated a 100% negative predictive value for probable AD, meaning no AD patients had zero smell errors.

Conclusions:

• Olfactory testing can aid in ruling out probable AD in patients with cognitive impairment.
• However, the sensitivity of olfactory testing for diagnosing probable AD remains limited.