The relation between tau, amyloid and cognition has yet to be fully defined. Using flortaucipir (18F-AV-1451) PET tau imaging in patients with varying amyloid and cognitive status, Pontecorvo et al. suggest that development of tau beyond the mesial temporal lobe is associated with, and may be dependent on, amyloid accumulation.

Using flortaucipir, Pontecorvo et al. reveal an increase in cortical tau over 18 months in Aβ+ but not Aβ- subjects, and an association between baseline tau and the magnitude of changes in tau and cognitive performance. The abundance and distribution of tau may influence both tau spreading and cognitive decline.

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Aims: To evaluate the impact of amyloid PET imaging on diagnosis and patient management in a multicenter, randomized, controlled study. Methods: Physicians identified patients seeking a diagnosis for mild cognitive impairment or dementia, possibly due to Alzheimer disease (AD), and recorded a working diagnosis and a management plan. The patients underwent florbetapir PET scanning and were randomized to either immediate or delayed (1-year) feedback regarding amyloid status. At the 3-month visit, the physician updated the diagnosis and recorded a summary of the actual patient management since the post-scan visit. The study examined the impact of immediate versus delayed feedback on patient diagnosis/management at 3 and 12 months. Results: A total of 618 subjects were randomized (1:1) to immediate or delayed feedback arms, and 602 subjects completed the 3-month primary endpoint visit. A higher proportion of patients in the immediate feedback arm showed a change in diagnosis compared to the controls (32.6 vs. 6.4%; p = 0.0001). Similarly, a higher proportion of patients receiving immediate feedback had a change in management plan (68 vs. 55.5%; p < 0.002), mainly driven by changes in AD medication. Specifically, acetylcholinesterase inhibitors were prescribed to 67% of the amyloid-positive and 27% of the amyloid-negative subjects in the information group compared with 56 and 43%, respectively, in the control group (p < 0.0001). These between-group differences persisted until the 12-month visit. Conclusion: Knowledge of the amyloid status affects the diagnosis and alters patient management.