Will PET amyloid imaging lead to overdiagnosis of Alzheimer dementia?

The End of the Beginning of the Alzheimer's Disease Nightmare: A Devil's Advocate's View

Although there have been so many failures in Alzheimer's disease (AD) modifying trials, there are still many compounds in the pipeline and the hope still remains that the entrance of disease-modifying treatment (DMT) for AD will positively and dramatically change the whole situation of AD treatment. However, if DMT does enter the market, it will be the beginning of a great number of challenges and problems. The current infrastructure for diagnostics of early (pre-dementia) AD does not have the capacity to meet the demands and expectations of the population. Neither is there capacity for treatment monitoring and follow-ups. If screening is considered, there will be a great risk for false positive cases and a great number of people who will have to undergo diagnostics. There will be high costs for diagnostics and treatment initially, while potential benefits will occur much later in other sectors than where the payers for treatment are. Although there are great hopes that prevention of cardiovascular risk factors and changes in lifestyle might impact the risk for dementia, there is still no consensus that this is the case. Finally, the relevance of different AD paradigms such as amyloid and tau is still a matter of discussion, particularly regarding the oldest old.

Nanoparticles as contrast agents for brain nuclear magnetic resonance imaging in Alzheimer's disease diagnosis

Nuclear Magnetic Resonance Imaging (MRI) of amyloid plaques is a powerful non-invasive approach for the early and accurate diagnosis of Alzheimer's disease (AD) along with clinical observations of behavioral changes and cognitive impairment. The present article aims at giving a critical and comprehensive review of recent advances in the development of nanoparticle-based contrast agents for brain MRI. Nanoparticles considered for the MRI of AD must comply with a highly stringent set of requirements including low toxicity and the ability to cross the blood-brain-barrier. In addition, to reach an optimal signal-to-noise ratio, they must exhibit a specific ability to target amyloid plaques, which can be achieved by grafting antibodies, peptides or small molecules. Finally, we propose to consider new directions for the future of MRI in the context of Alzheimer's disease, in particular by enhancing the performances of contrast agents and by including therapeutic functionalities following a theranostic strategy.

Critical review of the Appropriate Use Criteria for amyloid imaging: Effect on diagnosis and patient care

INTRODUCTION

The utility of the Appropriate Use Criteria (AUC) for amyloid imaging is not established.

METHODS

Fifty-three cognitively impaired patients with clinical F18-florbetapir imaging were classified as early and late onset, as well as AUC-consistent or AUC-inconsistent. Chi-square statistics and t test were used to compare demographic characteristics and clinical outcomes as appropriate.

RESULTS

Early-onset patients were more likely to be amyloid positive. Change in diagnosis was more frequent in late-onset cases. Change in therapy was more common in early-onset cases. AUC-consistent and AUC-inconsistent cases had comparable rates of amyloid positivity. We saw no difference in the rate of treatment changes in the AUC-consistent group as opposed to the AUC-inconsistent group.

DISCUSSION

The primary role of amyloid imaging in the early-onset group was to confirm the clinically suspected etiology, and in the late-onset group in detecting amyloid-negative cases. The rate of therapeutic changes was significantly greater in the early-onset cases.

Drug repurposing for vascular dementia: overview and current developments

Antidementive drugs have made Alzheimer's disease a symptomatically treatable condition but have essentially bypassed vascular dementia. The complexity of its pathology, the variable pathognomonic manifestations, the absence of validated biomarkers and the continuum with Alzheimer's disease that makes vascular dementia a comparatively small market are the major contributing factors. This report discusses how drug repurposing can be harnessed to identify new therapeutic opportunities, where such efforts are already yielding promising results, and which ones must be considered failures. Most investigations address obvious aspects cerebral small vessel disease, but some early-stage developments attempt changes in gene expression or modulation of complex biological pathways. A stronger focus on the nature and dynamics of white matter lesions should yield additional molecular targets.