ABSTRACT
BACKGROUND: Odor identification deficits occur in Alzheimer's disease (AD), as measured by the 40-item University of Pennsylvania Smell Identification Test (UPSIT). OBJECTIVE: To determine if UPSIT scores predict amyloid-ß (Aß) status, determined by 11C-Pittsburgh Compound B PET. We also compared UPSIT scores to Aß status in predicting future memory decline. METHODS: Subjects were recruited into a longitudinal clinical prediction study. We analyzed data from those who had UPSIT, cognitive testing, PIB PET, and at least 12 months' clinical follow-up. Forty-six amnestic mild cognitive impairment patients and 25 cognitively normal controls were included. Amyloid-positivity was defined as composite PIB standardized uptake value ratio >1.5. Logistic regression and Receiver Operating Characteristic Curve analyses tested the predictive utility of impaired olfaction (defined as UPSIT score <35) and amyloid-positivity for memory decline. RESULTS: High UPSIT scores predicted absence of amyloidosis on PET, with negative predictive value of 100%. Positive predictive value of low UPSIT scores on positive Aß status was only 41%. Both low UPSIT score (ORâ=â4.301, 95% CIâ=â1.248, 14.821, pâ=â0.021) and positive PET scan (ORâ=â20.898, 95% CIâ=â2.222, 196.581, pâ=â0.008) predicted memory decline. CONCLUSION: Individuals with high UPSIT scores are less likely to have cerebral amyloidosis or experience memory decline. Therefore, UPSIT has potential as a screening tool to determine utility of Aß PET in clinical practice or enrollment in clinical trials. Low UPSIT score is a non-specific marker of neurodegeneration that could indicate further workup in patients with memory complaints.
