Abstract

Objective: This study compares Amyloid β (Aβ) PET positive and negative patients with their neuropsychological profiles. A definitive link exists between Aβ deposits and cognitive disorders such as MCI or Alzheimer’s disease (AD), but imaging tests based on Aβ’s clinical context might be unjustified and could be cost-prohibitive.

Background: Amnestic MCI is considered prodromal to AD/dementia in a majority of cases. Many studies have shown a positive correlation between Aβ PET positive individuals and their likelihood to progress to AD. Aβ deposits in the brain are not always a sign of AD or even MCI, and many elderly people live normal lives with elevated levels. The presence of Aβ in the brain should be carefully considered alongside other tests before making a clinical diagnosis of MCI or AD.

Methods: 130 subjects from Barrow Neurological Institute (Phoenix, AZ) were included in this study. Amyloid PET report data was pulled from Dignity Health St. Joseph’s Hospital and Medical Center Outpatient Imaging. All data was anonymized and categorized into positive amyloid PET, negative amyloid PET, and clinical diagnosis based on neuropsychological profiles.
Results: The demographic data indicates that 38.5% of the 91 patients diagnosed as amnestic MCI were amyloid PET negative, and 61.5% were amyloid PET positive. Of the 39 patients diagnosed as Dementia or AD 15.4% were amyloid PET negative and 84.6% were amyloid PET positive. Correlational analysis between diagnosis and neuropsychological variables suggests that some variables correlate well, while others do not.

Conclusion: This study indicates that PET is still a clinical indicator of MCI or dementia/AD, but it has its exceptions. A small number of patients diagnosed as dementia/AD had a negative amyloid PET suggesting that beta amyloid plaques are not the only cause of the disease.

Keywords: Mild Cognitive Impairment (MCI); Amnestic MCI; Positron Emission Tomography (PET); Amyloid PET; Neuropsychological testing