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

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.