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Conversion of amyloid positive and negative MCI to AD over 3 years: an 11C-PIB PET study
A Okello1, J Koivunen, P Edison
1Division of Neuroscience and Mental Health, Faculty of Medicine, Imperial College London, UK.
Background:
Patients with amnestic mild cognitive impairment (MCI) represent an important clinical group as they are at increased risk of developing Alzheimer disease (AD). (11)C-PIB PET is an in vivo marker of brain amyloid load.
Objective:
To assess the rates of conversion of MCI to AD during a 3-year follow-up period and to compare levels of amyloid deposition between MCI converters and nonconverters.
Methods:
Thirty-one subjects with MCI with baseline (11)C-PIB PET, MRI, and neuropsychometry have been clinically followed up for 1 to 3 years (2.68 +/- 0.6 years). Raised cortical (11)C-PIB binding in subjects with MCI was detected with region of interest analysis and statistical parametric mapping.
Results:
Seventeen of 31 (55%) subjects with MCI had increased (11)C-PIB retention at baseline and 14 of these 17 (82%) clinically converted to AD during follow-up. Only one of the 14 PIB-negative MCI cases converted to AD. Of the PIB-positive subjects with MCI, half (47%) converted to AD within 1 year of baseline PIB PET, these faster converters having higher tracer-retention values than slower converters in the anterior cingulate (p = 0.027) and frontal cortex (p = 0.031). Seven of 17 (41%) subjects with MCI with known APOE status were epsilon4 allele carriers, this genotype being associated with faster conversion rates in PIB-positive subjects with MCI (p = 0.035).
Conclusions:
PIB-positive subjects with mild cognitive impairment (MCI) are significantly more likely to convert to AD than PIB-negative patients, faster converters having higher PIB retention levels at baseline than slower converters. In vivo detection of amyloid deposition in MCI with PIB PET provides useful prognostic information.
Insights
Patients with mild cognitive impairment (MCI) who show amyloid buildup via (11)C-PIB PET scans are significantly more likely to develop Alzheimer's disease (AD). Higher amyloid levels indicate faster conversion to AD.
Area of Science:
- Neuroscience
- Medical Imaging
- Gerontology
Background:
- Mild cognitive impairment (MCI) increases Alzheimer's disease (AD) risk.
- Amyloid deposition is a key biomarker for AD.
- (11)C-PIB PET offers in vivo visualization of brain amyloid load.
Purpose of the Study:
- Assess MCI to AD conversion rates over 3 years.
- Compare amyloid deposition levels in MCI converters versus non-converters.
- Evaluate (11)C-PIB PET as a prognostic tool for MCI.
Main Methods:
- Followed 31 MCI subjects for 1-3 years.
- Utilized baseline (11)C-PIB PET, MRI, and neuropsychometry.
- Analyzed cortical (11)C-PIB binding using ROI analysis and SPM.
Main Results:
- 55% of MCI subjects had elevated baseline (11)C-PIB retention.
- 82% of PIB-positive MCI subjects converted to AD within follow-up.
- Faster converters showed higher PIB retention in specific brain regions; APOE4 carriers converted faster.
Conclusions:
- PIB-positive MCI patients have a higher likelihood of converting to AD.
- Higher baseline PIB retention correlates with faster conversion to AD.
- (11)C-PIB PET provides valuable prognostic information for MCI patients.
