Ossenkoppele R, et al. – Researchers conducted a cross-sectional study of 719 participants recruited from three dementia centers in South Korea, Sweden, and the United States (June 2014-November 2017) to investigate the discriminative accuracy of [¹⁸F]flortaucipir for Alzheimer’s disease (AD) vs non-AD neurodegenerative disorders. Researchers reported that [¹⁸F]flortaucipir positron emission tomography (PET) scan was able to distinguish AD from other neurodegenerative diseases.

Methods

• Investigators enrolled study participants (N=719) from three dementia centers in South Korea, Sweden, and the United States between June 2014 and November 2017. Study participants included: cognitive normal control participants (n=160); individuals with mild cognitive impairment (MCI; n=126), of whom 65.9% were amyloid-β positive (ie, MCI due to AD); individuals with AD dementia (n=179); and those with various non-AD neurodegenerative disorders (n=254).
• The index test was the [¹⁸F]flortaucipir PET standardized uptake value ratio (SUVR) in five predefined regions of interest.
• The reference standard was the clinical diagnosis determined at the specialized memory centers.
• The discriminative accuracy (ie, sensitivity and specificity) of [¹⁸F]flortaucipir was examined for AD dementia compared to all non-AD neurodegenerative disorders in the primary analysis.
• The area under the curve (AUC) of [¹⁸F]flortaucipir SUVR was compared to three established magnetic resonance imaging (MRI) measures (hippocampal volumes and AD signature and whole-brain cortical thickness), and sensitivity and specificity of [¹⁸F]flortaucipir in MCI due to AD compared to non-AD neurodegenerative disorders were determined in secondary analyses.

Results

• The overall mean (standard deviation) age of study participants was 68.8 (9.2) years, and 48.4% were male.
• Study results showed that the proportions of patients who were amyloid-β positive were 26.3%, 65.9%, 100%, and 23.8% among cognitively normal controls, patients with MCI, patients with AD dementia, and patients with non-AD neurodegenerative disorders, respectively.
• Researchers reported that [¹⁸F]flortaucipir uptake in the medial-basal and lateral temporal cortex exhibited 89.9% (95% CI: 84.6% to 93.9%) sensitivity and 90.6% (95% CI: 86.3% to 93.9%) specificity using the threshold based on controls (SUVR, 1.34), and 96.8% (95% CI: 92.0% to 99.1%) sensitivity and 87.9% (95% CI: 81.9% to 92.4%) specificity using the Youden Index–derived cutoff (SUVR, 1.27) for distinguishing AD dementia from all non-AD neurodegenerative disorders.
• Compared with the three volumetric MRI measures (AUC range, 0.63-0.75; all ROIs P < 0.001), the AUCs for all five [¹⁸F]flortaucipir ROIs were higher (AUC range, 0.92-0.95).
• It was noted that diagnostic performance of the five [¹⁸F]flortaucipir ROIs were lower in MCI due to AD (AUC range, 0.75-0.84).