Combination of amyloid and FDG PET for the prediction of short-term conversion from MCI to Alzheimer´s disease in the clinical practice

Abstract

Purpose: Amnestic mild cognitive impairment (aMCI) is considered a precursor to Alzheimer’s disease (AD). Since cerebral amyloid aggregation and neurodegeneration can be detected at an early stage, it can serve as a diagnostic aid. This study aimed to determine the predictive value of Amyloid-PET and FDG-PET in determining progression to AD among patients with aMCI. Methods: This study recruited 145 patients with aMCI from October 2013 to March 2021. The patients were classified into four groups based on whether Amyloid-PET (A) and FDG-PET (N) were positive (+) or negative (-). The patients were then clinically followed to establish progression to dementia due to AD. Results: Amyloid-PET demonstrated high sensitivity (100% in year 1, 94.67% in year 4) and a high negative predictive value (100% in year 1, 88.24% in year 4). FDG-PET exhibited a high negative predictive value initially (94.59% in year 1), and during follow-up, both specificity (85%) and positive predictive value (88%) increased. The conversion from aMCI to AD had a global mean time of 39.95 months. However, progression to AD was slower in amyloid-negative patients versus amyloid-positive patients (75.07 [CI 56.54–81] vs. 32.59 months [CI 20.56–40.74] months). Taking both tests together, the time to conversion was faster in A+/N + versus A+/N- patients (27.79 [CI 20.40–33.21] vs. 37.38 [CI 20.73–48.26] months). Conclusions: Among patients with aMCI, those with a positive Amyloid-PET and an AD pattern on FDG-PET progressed to dementia significantly earlier versus those with a positive Amyloid-PET only. Using both biomarkers during the initial diagnosis enhances the prediction of short-term conversion. Clinical trial number: Not applicable. It is not a clinical trial.