The results of a study published in JAMA showed that [18F]flortaucipir positron emission tomography (PET) was able to differentiate Alzheimer disease (AD) from other neurodegenerative disorders. The multicenter, cross-sectional study was conducted at 3 dementia centers: 1 each in South Korea, Sweden, and the United States.
The investigators sought to examine the discriminative accuracy of [18F]flortaucipir PET for the diagnosis of AD vs non-AD neurodegenerative diseases. A total of 719 participants were recruited for the study between June 2014 and November 2017 and were grouped as follows: cognitively normal control participants (n=160); patients with mild cognitive impairment (MCI), of whom 65.9% tested positive for amyloid β (ie, MCI because of AD) (n=126); patients with AD dementia (n=179); and patients with a variety of non-AD neurodegenerative disorders (n=254).
The reference standard used in this study was the clinical diagnosis established at the 3 specialized memory centers. The primary analysis examined the discriminative accuracy — that is, the sensitivity and specificity — of [18F]flortaucipir for AD dementia vs all non-AD neurodegenerative diseases. The secondary analysis compared the area under the curve (AUC) of [18F]flortaucipir standardized uptake value ratio (SUVR) with 3 established magnetic resonance imaging measures (ie, hippocampal volumes, AD signature, and whole-brain cortical thickness). In addition, the sensitivity and specificity of [18F]flortaucipir in MCI because of AD vs non-AD neurodegenerative disorders were established.
The mean age of the participants was 68.8±9.2 years; 48.4% of the patients were men. The proportions of individuals who were amyloid β-positive were as follows: 26.3% among cognitively normal individuals , 65.9% among patients with MCI , 100% among patients with AD dementia , and 23.8% among patients with non-AD neurodegenerative disorders.
[18F]flortaucipir uptake in the medial-basal and lateral temporal cortex revealed 89.9% (95% CI, 84.6%-93.9%) sensitivity and 90.6% (95% CI, 86.3%-93.9%) specificity using the threshold according to control participants (SUVR, 1.34) for distinguishing AD from all non-AD neurodegenerative disorders. In contrast, the values were 96.8% (95% CI, 92.0%-99.1%) sensitivity and 87.9% (95% CI, 81.9%-92.4%) specificity using the Youden index-derived cutoff (SUVR, 1.27) for discriminating AD dementia from all non-AD neurodegenerative diseases.
The AUCs for the 5 [18F]flortaucipir predefined regions of interest (ROIs) were significantly higher (AUC range, 0.92-0.95) than for the 3 volumetric magnetic resonance imaging measures (AUC range, 0.63-0.75; P <.001 for all ROIs). The diagnostic performance of the 5 [18F]flortaucipir ROIs was lower in patients with MCI because of AD (AUC range, 0.75-0.84).
The investigators concluded that the accuracy and potential use of [18F]flortaucipir PET in patient care warrant additional research in populations of patients that are more clinically representative.
Ossenkoppele R, Rabinovici GD, Smith R, et al. Discriminative accuracy of [18F]flortaucipir positron emission tomography for Alzheimer disease vs other neurodegenerative disorders. JAMA. 2018;320(11):1151-1162.