Properties of odor identification testing in screening for early-stage Alzheimer’s disease

Abstract

Odor identification (OI) is impaired in the early stages of Alzheimer’s disease (AD). However, data regarding the diagnostic properties of OI tests are lacking, preventing their clinical use. We aimed to explore OI and determine the accuracy of OI testing in screening for patients with early AD. In total, 30 participants with mild cognitive impairment due to AD (MCI-AD), 30 with mild dementia due to AD (MD-AD), and 30 cognitively normal elderly participants (CN) were enrolled, and cognitive examination (CDR, MMSE, ADAS-Cog 13, and verbal fluency tests) and assessment of OI (Burghart Sniffin’ Sticks odor identification test) were performed. MCI-AD patients scored significantly worse in OI than CN participants, and MD-AD patients had worse OI scores than MCI-AD patients. The ratio of OI to ADAS-Cog 13 score had good diagnostic accuracy in differentiating AD patients from CN participants and in differentiating MCI-AD patients from CN participants. Substitution of ADAS-Cog 13 score with the ratio of OI to ADAS-Cog 13 score in a multinomial regression model improved the classification accuracy, especially of MCI-AD cases. Our results confirmed that OI is impaired during the prodromal stage of AD. OI testing has a good diagnostic quality and can improve the accuracy of screening for early-stage AD.

Odor identification score as an alternative method for early identification of amyloidogenesis in Alzheimer’s disease

“…Furthermore, the odor identification score has been reported to possess superior performance when distinguishing between AD and healthy participants compared to between stages of AD 26 . The odor identification score excelled in differentiating between healthy controls and prodromal AD (AUC = 0.908) but was not as effective in distinguishing between prodromal AD and AD dementia (AUC = 0.773) 27 . These findings show that odor identification scores are highly sensitive in the early stages of AD but may not be as suitable for monitoring disease progression 27 .…”

“…The odor identification score excelled in differentiating between healthy controls and prodromal AD (AUC = 0.908) but was not as effective in distinguishing between prodromal AD and AD dementia (AUC = 0.773) 27 . These findings show that odor identification scores are highly sensitive in the early stages of AD but may not be as suitable for monitoring disease progression 27 . High scores on the 40-item University of Pennsylvania Smell Identification Test are typically linked to a negative amyloid PET scan result 28 .…”