The impact of amyloid‐PET and FDG‐PET on the progression from amnestic MCI to AD dementia in clinical practice

Abstract

AbstractBackgroundAlzheimer disease (AD) is the most common cause of dementia worldwide. It is known that cerebral amyloid aggregation and neurodegeneration are first steps in the physiopathology of AD. In the prodromal phase, a clinical diagnosis of amnesic mild cognitive impairment (aMCI) can be stablished, but not all subjects with MCI have a prodromal AD. The objective of this study was to determinate the impact of amyloid and FDG PET on the progression from aMCI to AD dementia.MethodsFrom October 2013 to March 2021, we prospectively selected 145 patients with a diagnosis aMCI. We excluded subjects older than 85 and those with structural brain lesion on brain MRI. Participants went through an amyloid and an FDG‐PET scans and were classified as positive or negative for amyloid and neurodegeneration. Patients were followed to stablish progression to AD dementia, 118 patients were followed up more than 36 months. Statistical analyses were done with STATA with significance set at p<0.05. All analyses were adjusted by age, gender, and education.ResultsDemographics are shown on table 1. Sensibility, specificity, negative predictive value, and positive predictive value during the 4 years are shown on table 2. 88 patients were A+ and 74 patients were A‐. We divided the patients in 4 groups: A+/FDG+ (n:54), A+/FDG‐ (n:34), A‐/FDG‐ (40), A‐/FDG+(4). The mean of conversion were 39.95 months, this time depends on the result of the biomarkers. A‐ patients converted less and latter with a mean of 75.07 (IC 56.54→81) month, than A+ patients, that converted earlier (chi2 = 20.37 Pr>chi2 = 0.0000). A+/FDG+ converted with a mean of 27.79 (20.40‐33.21) months while A+/FDG‐ converted earlier with a mean of 37.38 (20.73‐48.26) month. (chi2 = 4.16 Pr>chi2 = 0.0415).ConclusionsAmyloid and FDG PET can help us to stablish prognosis in aMCI patients. We have observed that a positive amyloid PET is associated with an increased risk of progression to AD dementia. Even more, aMCI patients with both, amyloid PET and FDG, positive PETs progressed more often and earlier to AD dementia than those who have a positive amyloid PET but a negative FDG‐PET.